-NRLF 


/v-^  •  •• 

^=^V 


LIBRARY 

OF  THE  ^ 

UNIVERSITY  OF  CALIFORNIA. 


BIOLOGY 
LIBRARY 


Class  (  • 


AMERICAN  SCIENCE  SERIES 


ZOOLOGY 


FOR 


HIGH  SCHOOLS  AND   COLLEGES 


BY 


A.  S.   PACKARD,  JR.,  M.D.,  PH.D. 

MKMJ1KK    OP   TIIK    NATIONAL   ACADEMY   OP   SCIENCES  ;    PROFESSOR  OP   ZOOLOGY 
AND   GEOLOGY   IN    BROWN   UNIVERSITY. 


SECOND  EDITION,   REVISED 

L  IlUt  All  Y 

UNI',  J||  i  TV 


NEW   YORK 
HENRY  HOLT  AND   COMPANY 

1880 


Copyright,  1879, 

BY 

HENKY  HOLT  &  Co. 


THE  JOHN  A.  GRAY  PRESS, 

AND  STEAM  TYPE-SETTING  OFFICE, 

Cor.  Frankfort  and  Jacob  Sts., 

NEW  YORK. 


PREFACE. 


THIS  book  is  designed  to  be  used  quite  as  much  in  the  la- 
boratory or  with  specimens  in  hand,  as  in  the  class-room.  If 
Zoology  is  to  be  studied  as  a  mental  discipline,  or  even  if  the 
student  desires  simply  to  get  at  a  genuine  knowledge,  at  first 
hand,  of  the  structure  of  the  leading  types  of  animal  life, 
he  must  examine  living  animals,  watch  their  movements  and 
habits,  and  finally  dissect  them,  as  well  as  study  their  mode 
of  growth  before  and  after  leaving  the  egg  or  the  parent,  as 
the  case  may  be.  But  the  young  student  in  a  few  weeks' 
study  in  the  laboratory  cannot  learn  all  the  principles  of  the 
science.  Hence,  he  needs  a  teacher,  a  guide,  or  at  least  a 
manual  of  instruction.  This  work  is  an  expansion  of  a 
course  of  lectures  for  college  students,  but  has  been  pre- 
pared to  suit  the  wants  of  the  general  reader  who  would  ob- 
tain some  idea  of  the  principles  of  the  science  as  generally 
accepted  by  advanced  zoologists,  in  order  that  he  may  under- 
stand the  philosophical  discussions  and  writings  relating  to 
modern  doctrines  of  biology,  especially  the  law  of  evolution 
and  the  relations  between  animals  and  their  surroundings. 

The  book  has  been  prepared,  so  far  as  possible,  on  the  in- 
ductive method.  The  student  is  presented  first  with  the 
facts ;  is  led  to  a  thorough  study  of  a  few  typical  forms, 
taught  to  compare  these  with  others,  and  finally  led  to  the 
principles  or  inductions  growing  out  of  the  facts.  He  has 
not  been  assailed  with  a  number  of  definitions  or  diagnoses 
applicable  to  the  entire  group  to  which  the  type  may  belong 
before  he  has  learned  something  about  the  animals  typical 

1741 


iv  PREFACE, 

of  the  order  or  class  ;  but  these  are  placed  after  a  description 
of  one  or  a  few  examples  of  the  group  to  which  they  may 
belong.  The  simplest,  most  elementary  forms  are  first  no- 
ticed, beginning  with  the  Protozoa  and  ending  with  the  Ver- 
tebrates. In  working  up  from  the  simplest  forms  to  those 
more  complex,  it  is  believed  that  this  is  the  more  logical  and 
philosophical  method,  and  that  in  this  way  the  beginner  in  the 
science  can  better  appreciate  the  gradual  unfolding  of  the  lines 
of  animal  forms  which  converge  toward  his  own  species,  the 
flower  and  synthesis  of  organic  life.  Still  the  learner  is  ad- 
vised to  begin  his  work  by  a  study  of  the  first  part  of  Chap- 
ter VIII. ,  on  Vertebrates,  and  to  master,  with  a  specimen  in 
hand,  the  description  of  the  frog,  in  order  that  he  may  have 
a  standard  of  comparison,  a  point  of  departure,  from  which 
to  survey  the  lower  forms. 

Particular  attention  has  been  given  to  the  development  of 
animals,  as  this  subject  has  been  usually  neglected  in  such 
manuals.  Some  original  matter  is  introduced  into  the  book  ; 
a  new  classification  of  the  Crustacea  is  proposed,  the  orders 
being  grouped  into  the  subclasses  Neocarida  and  Palceocar- 
ida.  Most  of  the  anatomical  descriptions  and  drawings 
have  been  made  expressly  for  this  book,  and  here  the  author 
wishes  to  acknowledge  the  essential  aid  rendered  by  Dr.  C.  S. 
Minot,  who  has  prepared  the  drawings  and  descriptions  of 
the  fish,  frog,  snake,  turtle,  pigeon,  and  cat. 

In  compiling  the  book,  the  author  has  freely  used  the 
larger  works  of  Gegenbaur,  Huxley,  Peters  and  Carus,  Claus, 
Rolleston,  and  others,  whose  works  are  enumerated  at  the 
end  of  the  volume,  and  in  many  cases  he  has  paraphrased 
or  even  adopted  the  author's  language  verbatim  when  it  has 
suited  his  purpose.  Besides  these  general  works  many  mon- 
ographs and  articles  have  been  drawn  upon. 

In  order  to  secure  a  greater  accuracy  of  statement,  and  to 
render  the  work  more  authoritative  as  a  manual  of  Zoology, 


PREFACE.  v 

the  author  has  submitted  the  manuscript  of  certain  chapters 
to  naturalists  distinguished  by  their  special  knowledge  of 
certain  groups.  The  manuscript  of  the  sponges  has  been 
read  by  Professor  A.  Hyatt ;  of  the  worms  and  Mollusca,  by 
Dr.  Charles  S.  Minot ;  of  the  Echinoderms,  by  Mr.  Walter 
Faxon;  of  the  Crustacea,  by  Mr.  J.  S.  Kingsley.  Proofs  of  the 
part  relating  to  the  fishes  have  been  revised  by  Professor  T. 
Gill,  whose  classification  as  given  in  his  "Arrangement  of 
the  Families  of  Fishes,"  has  been  closely  followed,  his  defin- 
itions having  been  adopted  often  word  for  word.  The  man- 
uscript of  the  Batrachians  and  Reptiles  has  been  read  by 
Professor  E.  D.  Cope,  whose  classification,  given  in  his 
"  Check-List  of  North  American  Batrachia  and  Reptilia," 
has  been  adopted.  Proofs  of  the  part  on  birds  have  been 
read  by  Dr.  Elliott  Coues,  U.S.A.,  whose  admirable  "Key 
to  the  Birds  of  North  America"  has  been  freely  used,  the 
author's  words  having  been  often  adopted  without  quotation- 
marks.  Dr.  Coues  has  also  revised  the  proofs  of  the  pages  re- 
ferring to  the  Mammals.  To  the  friendly  aid  of  all  these 
gentlemen  the  author  is  deeply  indebted. 

As  to  the  illustrations,  which  have  been  liberally  provided 
by  the  publishers,  a  fair  proportion  are  original.  The  full- 
page  engravings  of  the  anatomy  of  the  typical  Vertebrates 
have  been  drawn  expressly  for  this  work  by  Dr.  C.  S.  Minot ; 
a  number  have  been  prepared  by  Mr.  J.  S.  Kingsley ;  Prof. 
W.  K.  Brooks  has  kindly  contributed  the  drawing  of  the 
nervous  system  and  otocyst  of  the  clam,  and  a  few  of  the 
sketches  are  by  the  author. 

The  publishers  are  indebted  to  Prof.  F.  V.  Hayden 
for  illustrations  kindly  loaned  from  the  Reports  of  the  U.  S. 
Geological  Survey  of  the  Territories ;  a  few  have  been 
loaned  by  Prof.  S.  F.  Baird,  U.S.  Commissioner  of  Fish  and 
Fisheries,  and  the  members  of  the  U.  S.  Entomological  Com- 
mission ;  a  number  have  been  loaned  by  the  Peabody  Acad- 


vi  PREFACE. 

emy  of  Science,  Salem,  Mass.;  by  the  publishers  of  the 
American  Naturalist,  and  by  the  Boston  Society  of  Natural 
History,  while  forty  of  the  cuts  of  birds  have  been  electro- 
typed  from  the  originals  of  Coues'  Key,  and  Tenney's  Zoology. 

Measurements  are  usually  given  in  the  metric  system  ;  in 
such  cases  the  approximate  equivalent  in  inches  and  fractions 
of  an  inch  being  added  in  parenthesis. 

Should  this  manual  aid  in  the  work  of  education,  stimu- 
late students  to  test  the  statements  presented  in  it  by  person- 
al observations,  and  thus  elicit  some  degree  of  the  inde- 
pendence and  self-reliance  characteristic  of  the  original  in- 
vestigator, and  also  lead  them  to  entertain  broad  views  in 
biology,  and  to  sympathize  with  the  more  advanced  and 
more  natural  ideas  now  taught  by  the  leading  biologists 
of  our  time,  the  author  will  feel  more  than  repaid. 

BROWN  UNIVERSITY, 

Providence,  R.  L,  October  25, 1879, 


PREFACE  TO  THE  SECOND  EDITION. 

A  NUMBER  of  changes  have  been  made  since  the  first  edi- 
tion, consisting  either  of  the  correction  of  errors,  or  the 
insertion  of  facts  new  to  science  since  the  book  was  written. 
Figures  of  the  opossum  and  its  marsupial  bone  have  been 
inserted  on  p.  575,  and  improved  illustrations  have  taken 
the  place  of  Figs.  400  and  492.     The  author   would   be 
thankful  for  the  communication  of  additional  errata  and 
suggestions  from  teachers  tending  towards  the  improve- 
icnt  of  the  book  ;  and  here  acknowledges,  with  thanks, 
rom  several  naturalists  in  revising  the  first  edition. 
July,  1880. 


CONTENTS. 


PAGE 

INTRODUCTION 1 

Definition  of  Zoology 1 

Morphology 5 

Organs  and  their  Functions 8 

Correlation  of  Organs 9 

Adaptation  of  Organs 10 

Analogy  and  Homology 12 

Physiology 12 

Psychology 12 

Reproduction 13 

Embryology 13 

Classification 13 

Zoogeography 16 

CHAPTER  I.   Branch  1.   PROTOZOA 17 

II.         "      2.   PORIFERA  (Sponges) 42 

III.  "      3.   CCELENTERATA  (Hydroids,  Jelly-fishes, 

and  Polyps) 51 

IV.  "      4.   ECHINODERMATA    (Crinoids,    Starfish, 

Sea  Urchins,  etc 96 

V.  "  5.  VERMES  (Worms) 138 

VI.  "  6.  MOLLUSCA  (Bivalves,  Snails,  Cuttles). . .  240 

VII.  "  7.  ARTHROPODA  (Crustaceans  and  Insects)  285 

VIII.  "  8.  VERTEBRATA .- 389 

IX.   COMPARATIVE  ANATOMY  OF  ORGANS 631 

Organs  of  Digestion,  the  Mouth  and  Teeth. . .  631 

Organs  of  Circulation 635 

Organs  of  Respiration 637 

The  Nervous  System, 638 

Organs  of  Sen'se 640 


viii  CONTENTS. 

FAGE 

CHAPTER  X.  DEVELOPMENT 644 

Metamorphosis C51 

Parthenogenesis  and  Alternation  of  Genera- 
tions   652 

Dimorphism  and  Polymorphism 654 

Individuality 656 

Hybridity 657 

XL  THE  GEOGRAPHICAL  DISTRIBUTION  OP  ANIMALS  658 

Means  of  Dispersal 660 

Division  of  the  Earth  into  Faunae 661 

Distribution  of  Marine  Animals 664 

Chief  Zoological  Fauna?  of  the  Earth,. 666 

XII.  THE  GEOLOGICAL  SUCCESSION  OP  ANIMALS 668 

XIII.  THE  ORIGIN  OF  SPECIES 671 

XIV.  PROTECTIVE  RESEMBLANCE 675 

XV.  INSTINCT  AND  REASON  IN  ANIMALS 680 

XVI.  GLOSSARY 689 

XVII.  INDEX .  697 


ZOOLOGY. 


INTRODUCTION. 

Definition  of  Zoology. — That  science  which  treats  of  liv- 
ing beings  is  called  Biology  (fiios,  life ;  Xoyos,  discourse). 
It  is  divided  into  Botany,  which  relates  to  plants,  and  Zo- 
ology ($c5ov,  animal ;  hdyot,  discourse),  the  science  treating 
of  animals. 

It  is  difficult  to  define  what  an  animal  is  as  distinguished 
from  a  plant,  when  we  consider  the  simplest  forms  of  either 
kingdom,  for  it  is  impossible  to  draw  hard  and  fast  lines  in 
nature.  In  defining  the  limits  between  the  animal  and 
vegetable  kingdoms,  our  ordinary  conception  of  what  a 
plant  or  an  animal  is  will  be  of  little  use  in  dealing  with 
the  lowest  forms  of  either  kingdom.  A  horse,  fish,  or 
worm  differs  from  an  elm  tree,  a  lily,  or  a  fern  in  having 
organs  of  sight,  of  hearing,  of  smell,  of  locomotion,  anc1 
special  organs  of  digestion,  circulation,  and  respration,  but 
these  plants  also  take  in  and  absorb  food,  have  a  circulation 
of  sap,  respire  through  their  leaves,  and  some  plants  are  me- 
chanically sensitive,  while  others  are  endowed  with  motion 
— certain  low  plants  such  as  diatoms,  etc.,  having  this 
power.  In  plants,  the  assimilation  of  food  goes  on  all  over 
the  organism,  the  transfer  of  the  sap  is  not  confined  to  any 
one  portion  or  set  of  organs  as  such.  It  is  always  easy  to 
distinguish  one  of  the  higher  plants  from  one  of  the  higher 
animals.  But  when  we  descend  to  animals  like  the  sea-ane- 
mones and  coral-polyps  which  were  called  Zoophytes  from 
their  general  resemblance  to  flowers,  so  striking  is  the  exter- 
nal similarity  between  the  two  kinds  of  organisms  that  the 


2  ZOOLOGY. 

early  observers  regarded  them  as  "  animal  flowers  ;"  and  in 
consequence  of  the  confused  notions  originally  held  in  regard 
to  them  the  term  Zoophytes  has  been  perpetuated  in  works 
on  systematic  zoology.  Even  at  the  present  day  the  com- 
pound Hydroids,  such  as  the  Sertularia,  are  gathered  and 
pressed  as  sea-mosses  by  many  persons  who  are  unobservant 
of  their  peculiarities,  and  unaware  of  the  complicated  anat- 
omy of  the  little  animals  filling  the  different  leaf-like  cells. 
Sponges  until  a  very  late  day  were  regarded  by  our  leading 
zoologists  as  plants.  The  most  accomplished  naturalists, 
however,  find  it  impossible  to  separate  by  any  definite  lines 
the  lowest  animals  and  plants.  So-called  plants,  as  Bacte- 
rium, and  so-called  animals,  as  Protamcela,  or  certain  mo- 
nads, which  are  simple  specks  of  protoplasm,  without  gen- 
uine organs,  may  be  referred  to  either  kingdom  ;  and,  in- 
deed, a  number  of  naturalists,  notably  Haeckel,  relegate 
to  a  neutral  kingdom  (the  Protista)  certain  low- 
est plants  and  animals.  Even  the  germs  (zo- 
ospores)  of  monads  like  Uvella  (Fig.  1),  and  those 
of  other  flagellate  infusoria,  may  be  mistaken 
for  the  spores  of  plants  ;  indeed,  the  active  fla- 
Pi  i  -Uvei-  grated  spores  of  plants  were  described  as  in- 
in'r  J?orianllaor  ^usor^a  ^7  Ehrenberg  ;  and  there  are  certain  so- 
monad,  with  called  flagellate  infusoria  so  much  like  low 

two   large    ci-      .  ,     °,  .,  -  _  . 

iia    called  plants  (such  as  the  red  snow,  or  Protococcus), 
magi  in   the  form,  deportment,  mode   of   reproduc- 


tion, and  appearance  of  the  spores,  that  even 
now  it  is  possible  that  certain  organisms  placed  among  them 
are  plants.  It  is  only  by  a  study  of  the  connecting  links 
between  these  lowest  organisms  leading  up  to  what  are  un- 
doubted animals  or  plants  that  we  are  enabled  to  refer  these 
beings  to  their  proper  kingdom. 

As  a  rule,  plants  have  no  special  organs  of  digestion  or 
circulation,  and  nothing  approaching  to  a  nervous  system. 
Most  plants  absorb  inorganic  food,  such  as  carbonic  acid 
gas,  water,  nitrate  of  ammonia,  and  some  phosphates,  silica, 
etc.  ;  all  of  these  substances  being  taken  up  in  minute  quan- 
tities. Low  fungi  live  on  dead  animal  matter,  and  promote 
the  process  of  putrefaction  and  decay,  but  the  food  of  these 


DISTINCTIONS  BETWEEN  ANIMALS  AND  PLANTS.     3 

organisms  is  inorganic  particles.  The  slime-moulds  called 
Myxomycetes,  however,  envelop  the  plant  or  low  animals, 
much  as  an  Amoeba  throws  itself  around  some  living  plant 
and  absorbs  its  protoplasm  ;  but  Myxomycetes,  in  their  man- 
ner of  taking  food,  are  an  exception  to  other  moulds.  The 
lowest  animals  swallow  other  living  animals  whole  or  in 
pieces  ;  certain  forms  like  Amoeba  (Fig.  2)  bore  into  minute 
algae  and  absorb  their  pro- 
toplasm ;  others  engulf  sili- 
cious-shelled  plants  (diatoms) 
absorbing  their  protoplasm. 
No  animal  swallows  silica, 
lime,  ammonia,  or  any  of 
the  phosphates  as  food.  On 

tlin  nfhov  lionrl  -nlnnfc  minii  Fig.  2. —Amoeba,  a  Protozoan.  Theright- 
tlie  Otliei  Hand,  piailtS  maill  -  han(fflgure  Bhows  three  pseudopodia on  the 
fnntnrp  or  nrnrliinp  from  in-  right  side;  in  the  two  other  figures  the 

pseudopodia  are  withdrawn  in  the  body- 

organic  matter  starch,  sugar  mass- 

and  nitrogenous  substances  which  constitute  the  food  of 
animals.  During  assimilation,  plants  absorb  carbonic  acid, 
and  in  sunlight  exhale  oxygen  ;  during  growth  and  work 
they,  like  animals,  consume  oxygen  and  exhale  carbonic  acid. 

Animals  move  and  have  special  organs  of  locomotion  ; 
few  plants  move,  though  some  climb,  and  minute  forms 
have  thread-like  processes  or  vibratile  lashes  (cilia)  resem- 
bling the  flagella  of  monads,  and  flowers  open  and  shut,  but 
these  motions  of  the  higher  plants  are  purely  mechanical, 
and  not  performed  by  special  organs  controlled  by  nerves. 
The  mode  of  reproduction  of  plants  and  animals,  however, 
is  fundamentally  identical,  and  in  this  respect  the  two  king- 
doms unite  more  closely  than  in  any  other.  Plants  also, 
like  animals,  are  formed  of  cells,  the  latter  in  the  higher 
forms  combined  into  tissues. 

As  the  lowest  plants  and  animals  are  scarcely  distinguish- 
able, it  is  probable  that  plants  and  animals  first  appeared 
contemporaneously  ;  and  while  plants  are  generally  said 
to  form  the  basis  of  animal  life,  this  is  only  partially  true  ; 
a  large  number  of  fungi  are  dependent  on  decaying  animal 
matter;  and  most  of  the  Protozoa  live  on  animal  food,  as 


4  ZOOLOGY. 

do  a  large  proportion  of  the  higher  animals.  The  two 
kingdoms  supplement  each  other,  are  mutually  dependent, 
and  prohably  appeared  simultaneously  in  the  beginning  of 
things.  It  should  be  observed,  however,  that  the  animal 
kingdom  overtops  the  vegetable  kingdom,  culminating  in 
man. 

In  speaking  as  we  have  of  low  animals  and  high  animals, 
we  are  comparing  very  unequal  quantities;  the  distance  be- 
tween monad  and  man  is  well-nigh  infinite.  But  there  is  a 
series  or  chain,  sometimes  broken  and  often  with  lost  links, 
connecting  the  extremes  ;  and  as  there  are  wide  differences 
in  form,  so  there  are  great  extremes  in  the  organs  and  de- 
gree of  complication  of  function  of  the  simple  as  compared 
with  the  more  complex  forms.  The  improvised  stomach  of 
an  Amoeba  is  not  comparable  with  the  stomach  of  an  hydra, 
nor  is  the  stomach  of  the  latter  creature  with  that  of  a 
horse  ;  ther.e  is  a  gradual  perfection  and  elaboration  or  spe- 
cialization of  the  stomach  as  we  ascend  in  the  animal  series. 
So  it  is  with  organs  of  locomotion  ;  the  pseudopods  and  cilia 
of  the  Protozoans  are  replaced  in  the  star-fishes  and  worms 
by  hollow  tentacles  or  various  fleshy  soft  appendages  ;  in 
crabs  and  insects  by  stiff,  jointed  limbs,  with  different  lev- 
erage systems  ;  and  these  are  replaced  in  vertebrates  by 
genuine  limbs  supported  by  bones.  A  comparative  view  of 
the  origin  and  structure  of  organs  succeeds  in  this  book  the 
systematic  account  of  the  animals  themselves. 

We  thus  see  that  the  organs  of  the  higher  animals  are 
merely  modifications  of  organs  often  having  the  same 
general  functions  as  in  the  lower  animals  ;  the  lower  or 
simpler  have  preceded  in  geological  history  the  higher  or 
more  specialized  forms,  and  thus  we  are,  in  ascending  the 
animal  series,  going  from  the  simple  to  the  complex.  For 
this  reason  the  plan  of  this  work  has  been  to  lead  the  stu- 
dent from  the  simpler  forms  of  animal  life  to  the  more 
complex  ;  and  though  the  vertebrate  animals,  such  as  fishes 
and  dogs,  are  more  familiar  and  interesting  to  us,  the  seri- 
ous student  of  zoology  will  feel  that  it  is  more  logical  and 
better  in  the  end  to  study  the  animal  world  in  the  order  in 
which  the  different  forms  have  appeared — as  we  believe, 


MORPHOLOGY.  5 

through  the  orderly  operations  of  physical  and  biological 
laws,  under  the  guidance  of  an  Infinite    Intelligence— a 
Creator  whose  modes  of  working  are  revealed  to  us  in  what 
we  call  the  laws  or  processes  of  nature. 
Zoology  is  subdivided  thus  : 

Morphology  or  gross  Anatomy,  and  minute 

Anatomy  (Histology). 
Physiology  and  Psychology. 


Zoology. 


Eeproduction  and  Embryology. 


Systematic  Zoology  or  Classification. 

Palaeontology. 

Zoogeography. 

Morphology. — In  order  to  properly  understand  Zoology, 
one  should  first  study  Morphology— i.e.,  the  general  struc- 
ture of  animals.  The  student  should  first  thoroughly  ac- 
quaint himself  with  the  anatomy  of  a  vertebrate  animal, 
such  as  a  frog,  as  compared  with  that  of  a  toad  or  salaman- 
der* The  examination  and  comparison  of  the  organs  of 
animals  belonging  to  distinct  groups,  is  called  Comparative 
Anatomy.  The  study  of  Morphology  also  includes  the  rela- 
tion of  the  different  organs  to  one  another,  and  of  all  to  the 
walls  of  the  body.  Finally,  we  need  also  to  study  the  com- 
position of  the  tissues  of  the  different  organs  ;  each  kind  of 
tissue  being  formed  of  different  kinds  of  elements  or  cells. 
This  department  of  Comparative  Anatomy  is  called  Histol- 
ogy (Greek,  iGrds,  web  or  tissue  ;  Ao;/o?,  discourse).  It 
treats  of  the  cell,  and  the  combination  of  cells  into  germ- 
layers,  tissues,  and  organs. 

The  Cell.— *The  primary  elements  of  the  bodies  of  animals 
are  called  cells.  They  are  microscopic  portions  of  proto- 
plasm either  with  or  without  a  wall.  Protoplasm  largely 
consists  of  protein,  which  is  a  complex  compound  of  car- 
bon, hydrogen,  oxygen,  and  nitrogen,  associated  with  a  large 
proportion  of  water.  Cells  are  originally  more  or  less 
spherical  sacs,  and  the  protoplasm  forming  the  cell-mass  is 
the  dynamic  part  of  the  cell.  The  protoplasm  of  animal  as 
well  as  vegetable  cells,  the  protoplasm  of  eggs  and  of  the 
cells  forming  the  different  tissues  of  the  animal  body,  as 


6  ZOOLOGY. 

well  as  the  entire  Amoeba  or  monad,  is  all  alike,  being  per- 
fectly homogeneous  to  the  chemist  or  microscopist  of  our 
day.  Yet  potentially  the  protoplasm  of  different  cells  exerts 
widely  different  forces  and  capabilities.  An  egg-cell  be- 
comes a  man,  whose  brain-cells  are  the  medium  of  the  intel- 
lectual power  which  enables  him  to  write  the  history  of 
his  own  species,  and  to  be  the  historian  of  the  forms  of  life 
which  stand  below  him.  The  cell  is  the  morphological 
unit  of  the  organic  world.  With  cells  the  biologist  can 
in  the  imagination  reconstruct  the  vegetable  and  animal 
worlds. 

The  primitive  form  of  a  cell,  when  without  a  nucleus  or 
nucleolus,  is  called  a  cytode  ;  genuine  cells  have  a  nucleus, 
the  latter  containing  a  nucleolus.  Animals  composed  of  but  a 
single  cell,  such  as  the  Amoeba  or  an  Inf  usorian,  are  said  to  be 
unicellular.  Cells  grow  by  absorbing  cell-food — i.e.,  by  the 
assimilation  of  matter  from  without,  and  this  matter  may  be 
in  masses  of  considerable  size  when  seen  under  the  microscope. 
Cells  multiply  by  self-division.  The  egg-cell  undergoes 
division  of  the  yolk  into  two,  four, 
eight,  and  afterward  many  cells ;  the 
cells  thus  formed  become  arranged  into 
two  layers  or  sets  called  germ-layers. 
The  outer  is  called  the  ectoderm  and 
the  inner  the  endoderm.  A  third  germ- 
layer  arises  between  them,  called  the 
_  3.-Gcrm  of  Saeitta.  mesoderm  or  middle  germ-layer.  From 

ec,  ectoderm  ;  en.  endoderm;  fl^/iop  trprm  lnvpr«  nv  PP!!  Imrnra  flio 
both  layers  formed  of  im-  tnese  ger  1-iayerS,  <  1-layerS,  tlie 

cieated  ceils.  tissues  of  the  body  are  formed,  such  as 

muscle,  bone,  nerve,  and  glandular  tissue.  These  tissues 
form  organs,  hence  animals  (as  well  as  plants)  are  called  or- 
ganisms, because  they  have  certain  parts  formed  of  a  partic- 
ular kind  of  tissue  set  apart  for  the  performance  of  a  special 
sort  of  work  or  physiological  labor.  This  separation  of 
parts  for  particular  or  special  functions  is  called  differentia- 
tion ;  and  the  highest  animals  are  those  whose  bodies  are 
most  differentiated,  while  the  lowest  are  those  whose  bodies 
are  least  differentiated  ;  hence  high  animals  are  specialized, 
and,  on  the  other  hand,  low  animals  are  simple.  Thus  dif- 


CELLS  AND   TISSUES.  7 

ferentiation  of  organs  involves  the  division  of  physiological 
labor. 

Tissues. — Of  the  different  kinds  of  tissues  there  is,  first, 
epithelial  tissue  (Fig.  4)  consisting  of  cells  with  a  nucleus  and 
nucleolus,  and  placed  side  by  side,  forming  a  layer.  All  the 
organs  develop  originally  from  epithelium,  which  is  the  prim- 
itive cell-structure  and  forms  the  tissues  of  the  germ-layers. 
Epithelial  cells  form  the  skin  of  animals,  and  also  the  lining 
of  the  digestive  canal.  The  cells  of  the  latter  may,  as  in 
sponges,  bear  a  general  resemblance  to  a  flagellate  infuso- 


Fig.  4.— Vertical  section  through  the  skin  of  an  embryonic  shark,  showing  at  E  the 
epithelial  cells,  forming  pavement  epithelfum ;  and  at  e,  columnar  epithelium. — After 
Gegenbaur. 

rian,  as  Codosiga,  or  they  may  each  bear  many  hairs,  called 
cilia,  which  by  their  constant  motion  maintain  currents  of 
the  fluids  passing  over  the  surface  of  the  epithelium.  The 
tissue  forming  glands  is  simply  modified  epithelium. 

Connective  tissue  is  formed  by  isolated  rounded  or  elon- 
gated cells  with  wide  spaces  between  them  filled  with  a  ge- 
latinous fluid  or  protoplasm,  and  occurs  between  muscles, 
etc.  This  tissue  forms  in  the  vertebrates  the  "  notochord  " 
—i.e.,  a  rod  supporting  the  bodies  of  vertebrate  embryos. 
Gelatinous  tissue  is  a  variety  of  connective  tissue  found  in 
the  umbrella  of  jelly-fishes  (Aurelia,  etc.).  Fibrous  and 
elastic  tissue  are  also  varieties  of  connective  tissue. 

Cartilaginous  tissue  is  characterized  by  cells  situated  in  a 


ZOOLOGY. 


Fig.  5.— Striated  muscular  flbrilla 
of  a  water  beetle.— After  Minot. 


still  firmer  intercellular  substance  ;  and  when  the  intercel- 
lular substance  becomes  combined  with  salts  of  lime  form- 
ing bone,  we  have  bony  tissue. 

The  blood-corpuscles  originate  from  the  mesoderm  as 
independent  cells  floating  in  the  circulating  fluid,  the  blood- 
cells  being  formed  contemporaneously  with  the  walls  of  the 
vessels  enclosing  the  blood.  In  the  invertebrates  the  blood- 
cells  are  either  strikingly  like  the  Amcela  in  appearance,  or 

are  oval,  but  still  capable  of 
changing  their  form.  Thus  blood- 
corpuscles  arise  like  other  tissues, 
except  that  the  blood-cells  are 
free. 

Muscular  tissue  is  also  composed  of  cells,  which  are  at 
first  nucleated  and  afterward  lose  their  nuclei.  From  being 
at  first  oval,  the  cells  finally  become  elongated  and  more  or 
less  spindle-shaped,  forming  fibres  ;  these  unite  into  bundles 
forming  muscles.  Each  fibre  is  ensheathed  in  a  membrane 
called  sarcolemma.  Muscular  fibres  may  be  simple  or  striated 
(Fig.  5).  The  contractility  of  muscles  is  due  to  the  con- 
tractility of  the  protdplasm 
originating  in  the  cells  forming 
the  fibres. 

Nervous  tissue  is  made  up 
of  nerve-cells  and  fibres  pro- 
ceeding from  them  ;  the  for- 
mer constituting  the  centres 
of  nervous  force,  and  usually 
massed  together,  forming  a 
ganglion  or  nerve-centre  from 
which  nerve-fibres  pass  to  the 

periphery  and  extremities  of  nerve8  (<?)  fft  *}  Proceedins  from  il- 
the  body,  and  serve  as  conductors  of  nerve-force  (Fig.  6). 
Organs  and  their  Functions.  —  Having  considered  the 
different  kinds  of  cells  and  the  tissues  they  form,  we  may 
now  consider  the  origin  of  organs  and  their  functions.  Tho 
Protamosba  may  be  considered  as  an  organless  being.  In 
Amceba  (Fig.  11)  we  first  meet  with  a  specialized  portion  of 
the  body,  set  apart  for  the  performance  of  a  special  function. 


in  the  clam,  with 


ORGANS  AND   THEIR  FUNCTIONS. 

Such  is  the  nucleus  ;  so  that  Amoeba  is  a  genuine  organism. 
Ascending  to  the  flagellate  Infusoria  (Fig.  1),  we  have  the 
flagella  developed  as  external,  permanent  organs  of  locomo- 
tion. In  the  Hydra  (Fig.  36)  the  tentacles  are  organs 
whose  functions  are  generalized.  In  the  worms  we  have  or- 
gans arranged  in  pairs  on  each  side  of  the  body,  and  in  gen- 
eral among  the  higher  invertebrates,  especially  the  crusta- 
ceans and  insects,  and  markedly  in  the  vertebrates,  we  have 
the  bilateral  symmetry  of  the  body  still  farther  emphasized 
in  the  nature  and  distribution  of  the  appendages. 

Of  the  internal  organs  of  the  body,  the  most  important  is 
the  digestive  cavity,  which  is  at  first  simple  and  primitive  in 
the  gastrula  or  embryo  of  all  many-celled  animals,  and  as  we 
ascend  in  the  animal  series  we  witness  its  gradual  special- 
ization, the  digestive  tract  being  differentiated  into  dis- 
tinct portions  (i.e.,  the  oesophagus,  stomach,  and  intestine), 
each  with  separate  functions  and  with  organs  of  respiration, 
digestion,  secretion,  and  excretion  set  apart  as  offshoots  or 
outgrowths  from  the  main  alimentary  tract.  In  like  man- 
ner the  skeleton  is  at  first  simple  and  afterward  is  extended 
into  the  different  organs,  the  various  parts  of  the  ap- 
pendicular  skeleton  corresponding  to  the  increased  flexi- 
bility and  diversified  leverage  power  ;  so  that  limbs  become 
subdivided  into  joints,  and  these  joints  still  further  subdi- 
vided as  we  go  from  the  points  of  attachment  to  the  peri- 
phery or  extremities,  as  seen  in  the  tendency  to  an  irrelative 
repetition  of  joints  in  the  limbs  and  feelers  of  crustaceans 
and  insects,  and  the  digits  of  the  lower  vertebrates. 

Correlation  of  Organs — Ouvier  established  this  princi- 
ple, showing  that  there  is  a  close  relation  between  the  forms 
of  the  hard  and  soft  parts  of  the  body,  together  with  the 
functions  they  perform,  and  the  habits  of  the  animal.  For 
example,  in  a  cat,  sharp  teeth  for  eating  flesh,  sharp  curved 
claws  for  seizing  smaller  animals,  and  great  muscular  activ- 
ity coexist  with  a  stomach  fitted  for  the  digestion  of  animal 
rather  than  vegetable  food.  So  in  the  ox,  broad  grinding 
teeth  for  triturating  grass,  cloven  hoofs  that  give  a  broad 
support  in  soft -ground,  and  a  several-chambered  stomach 
coexist  with  the  habits  and  instincts  of  a  ruminant.  Thus. 


10  ZOOLOGY. 

the  form  of  the  teeth  presupposes  either  a  ruminant  or  carni 
vore.  Hence  this  prime  law  of  comparative  anatomy  led  to 
the  establishment  by  Cuvier  of  the  fundamental  laws  of 
palaeontology,  by  which  the  comparative  anatomist  is  en- 
abled to  restore  from  isolated  teeth  or  bones  the  probable 
form  of  the  original  possessor.  Of  course  the  more  perfect 
the  series  of  bones  and  teeth,  or  the  more  complete  the  re- 
mains of  insects  or  mollusks,  the  more  perfect  will  be  our 
knowledge,  and  the  less  room  will  there  be  for  error  in  re- 
storing extinct  animals. 

Adaptation. — An  organ  with  a  certain  normal  use  or 
function  may  be  adapted,  in  consequence  of  a  change  in  the 
habits  of  the  animal,  to  another  use  than  the  original  one. 
To  take  an  extreme  case,  the  Anabas,  or  climbing  fish,  may 
use  its  fins  to  aid  it  in  ascending  trees.  On  the  other  hand, 
by  disuse  organs  become  aborted  or  rudimentary.  The 
teeth  of  the  whalebone  whale  are  rudimentary  in  the  young, 
and  are  replaced  by  whalebone,  which  is  more  useful  to  the 
animal ;  the  eyes  of  the  blind-fish  are  rudimentary,  func- 
tionless.  Those  of  certain  cave-insects  are  entirely  wanting, 
being  lost  through  disuse,  owing  to  a  change  of  life  from 
the  light,  outer  world  to  totally  dark  caverns,  and  the  con- 
sequent disuse  of  their  eyes.  Nature  is  economical.  Every 
thing  that  is  not  of  use  as  a  rule  disappears.  It  would  be  a 
waste  of  material  to  nourish  and  care  for  an  organ  in  a  cave- 
animal,  or  a  parasitic  insect  or  crustacean,  which  would  be 
of  no  use  to  the  animal.  On  the  other  hand,  if  the  leg  or 
tail  of  a  newt  is  snipped  off  by  some  rapacious  fish,  it 
grows  out  again. 

Moreover,  the  animal  organism  is  far  more  pliable  than  is 
generally  supposed.  Not  only  is  nature  continually  repair- 
ing wounds  and  waste,  not  only  is  the  body  being  contin- 
ually made  over  again,  but  certain  animals  undergo  a 
change  of  form,  either  generally  or  in  particular  parts.  If 
the  environment  is  unchanged,  the  animal  remains  true  to 
its  species.  The  dogma  of  the  invariability  or  stability  of 
species  is  a  fallacy.  Change  the  climate,  moisture  or  dryness, 
the  nature  of  the  soil ;  introduce  the  natural  enemies  of  the 
animal  or  remove  them  ;  destroy  the  balance  of  nature,  in 


LA  W  OF  INHERITANCE  AND  TRANSMISSION.        11 

other  words,  and  the  organism  changes.  The  plants  and 
animals  of  the  mummies  and  monuments  of  Egypt  are  prob- 
ably the  same  as  those  now  living  in  that  country,  because 
the  climate  and  soil  have  remained  the  same. 

The  assemblages  of  life  that  have  successively  peopled  the 
surface  of  the  earth,  and  which  are  geological  time-marks, 
have  probably  become  extinct  because  they  could  not  adapt 
themselves  to  more  or  less  rapid  oscillations  of  continents 
and  islands,  to  consequent  changes  of  climate  and  the  in- 
coming of  destructive  types  of  life.  This  probably  accounts 
for  the  origin,  culmination,  and  extinction  of  different 
types  of  life.  The  earth  has  been,  and  still  is,  in  a  state  of 
unstable  equilibrium.  Organic  life  has  been  and  is  even 
now,  in  a  degree,  being  constantly  readjusted  in  harmony 
with  these  changes  of  the  earth's  surface  and  climate.  Thus 
this  adaptation  of  organs  to  their  uses,  of  animals  to  their 
environment,  the  laws  controlling  the  origination  of  new 
forms  of  life  and  the  extinction  of  those  which  have  acted 
their  part  and  are  no  longer  of  service  in  the  economy  of 
nature,  is  part  of  the  general  course  of  nature,  and  evinces 
the  Infinite  Wisdom  and  Intelligence  pervading  and  contin- 
ually operating  in  the  universe.* 

Coupled  with  variability  is  the  law  of  inheritance  and 
transmission  of  variable  parts,  and  the  habits  thus  induced 
by  the  variation  of  parts.  It  should  be  observed  that  the 
portions  which  vary  most  are  the  peripheral  parts — i.e., 
fingers  and  toes,  tentacles  and  antennae,  the  skin  and  scales 
and  hair  ;  it  is  by  modifications  and  differences  brought 
about  in  those  parts  most  used  by  animals  that  the  multi- 
tudes of  specific  forms  have  resulted.  There  is,  as  Darwin 
stntes,  a  general  tendency  of  organisms  to  vary  ;  the  laws 
accounting  for  this  tendency  to  vary  have  yet  to  be  formu- 
lated ;  though  the  attempts  of  Lamarck  in  this  direction 
laid  the  way  for  the  discovery  and  application  of  the  funda- 

*  That  animals  and  plants  are  self -evolved,  that  the  world  has  made 
itself,  and  that  all  is  the  result  of  so-called  physical  and  biological  laws 
operating  from  within  outward,  is  as  inconceivable  as  the  medieval 
dogma  that  animals  and  plants  and  the  earth  they  inhabit  were  made 
in  the  twinkling  of  an  eye.  Sec  the  concluding  chapter  on  Evolution. 


12  ZOOLOGY. 

mental  laws  of  evolution.  On  the  other  hand,  pure  Dar- 
winism—viz., natural  selection— accounts  rather  for  the 
preservation  than  the  origination  of  the  forms  of  life. 

Analogy  and  Homology. — When  we  study  the  Inverte- 
brates alone  we  see  that  it  is  often  easy  to  trace  a  general 
identity  in  form  between  the  more  important  parts.  We 
notice  that  the  under  lip  of  a  worm  is  comparable  to  the  foot 
of  a  mollusk,  though  the  functions  of  these  parts  may  be 
quite  unlike  ;  these  are  therefore  examples  of  a  general 
identity  in  structure  or  homology  between  two  organs.  A 
closer  homology  implies  a  more  apparent  identity  of  form, 
as  seen  in  the  resemblance  in  structure  of  the  fore-limbs  of 
a  whale  and  a  seal,  or  the  pectoral  fins  of  fishes  and  the  fore- 
arms of  man. 

Analogy  implies  a  dissimilarity  of  structure  of  two  organs 
with  identity  in  use,  as  the  wing  of  an  insect  and  of  a  bird  ; 
the  leg  of  an  insect  and  the  leg  of  a  frog  ;  the  gill  of  a 
worm  and  the  gill  of  a  fish. 

Homology  implies  blood-relationship  ;  analogy  repudiates 
any  common  origin  of  the  organs,  however  physiologically 
alike.  The  most  general  homologies  are  those  existing  in 
organs  belonging  to  animals  of  different  branches  ;  the  most 
special  between  those  of  the  same  orders  and  minor  groups. 
Thus  it  is  fundamentally  a  question  of  near  or  remote  con- 
sanguinity. 

Physiology  treats  of  the  mode  in  which  organs  do  their 
work  ;  or,  in  other  words,  of  the  functions  of  different  or- 
gans. Thus  the  hand  grasps,  the  fins  of  a  fish  are  its  swim- 
ming organs  ;  the  function  of  the  nose  is  to  smell,  of  the 
liver  to  secrete  bile,  of  the  ovary  to  secrete  protoplasm 
which  forms  eggs. 

Psychology  is  the  study  of  the  instincts  and  reasoning 
powers  of  animals  ;  how  they  act  when  certain  parts  are 
irritated  ;  so  that  while  this  term  is  generally  applied  to 
man  alone,  Comparative  Psychology  deals  both  with  the 
simplest  automatic  acts  and  the  whole  series  of  psychic  pro- 
cesses— from  those  exercised  by  the  Protozoans,  such  as 
Amoeba,  up  to  the  complicated  instinctive  and  rational  acts 
of  man. 


REPRODUCTION  AND  EMBRYOLOGY.  13 

Reproduction. — The  simplest  form  of  reproduction  is 
cell-division,  one  cell  budding  or  separating  from  another. 
This  mode  of  growth  is  called  self-division  or  fission. 
Where  one  cell  separates  from  another,  the  separating  part 
being  smaller  than  the  original  cell,  or  where  a  number  of 
cells  separate  or  bud  out  from  a  many-celled  animal,  such  as 
a  Hydra,  the  process  is  called  gemmation.  A  third  mode  of 
reproduction  is  sexual,  the  sperm-cell  of  the  male  coalescing 
with  the  nucleus  of  the  egg  ;  the  commingling  of  the  pro- 
toplasm of  the  two  nuclei  resulting  in  a  series  of  events 
leading  to  the  formation  of  a  germ  or  embryo. 

Embryology  is,  strictly  speaking,  a  study  of  the  develop  • 
ment  of  animals  from  the  beginning  of  life  of  the  egg  up  to 
the  time  the  animal  leaves  the  egg  or  the  body  of  the  parent 
— namely,  up  to  the  time  when  it  begins  to  shift  for  itself  ; 
but  the  term  embryology  may  also  be  applied  to  the  grow- 
ing animal  from  the  egg  to  the  adult  condition.  Many  of 
the  lower  animals  undergo  a  metamorphosis,  suddenly  as- 
suming changes  in  form,  accompanied  by  changes  in  habits 
and  surroundings  ;  so  that  at  different  times  it  is,  so  to 
speak,  a  different  animal.  For  example,  the  caterpillar 
lives  on  solid  food,  crawls  on  the  ground,  and  has  a  worm- 
like  form  ;  it  changes  to  a  chrysalis  or  pupa,  lying  quies- 
cent, taking  no  food  ;  then  it  changes  to  a  butterfly  and 
flies  in  the  air,  either  taking  no  food  or  sipping  the  nectar 
of  flowers  :  in  all  these  three  stages  it  is  virtually  different 
animals  with  different  surroundings.  Many  animals  besides 
insects  have  a  metamorphosis,  and  their  young  are  called 
larvae  ;  thus  there  are  larval  polyps,  larval  star-fish,  larval 
worms — these  larvae  often  differing  remarkably  in  form, 
habits,  and  in  their  environment  or  surroundings,  as  com- 
pared with  the  mature  or  adult  forms. 

Classification. — After  thoroughly  studying  a  single  ani- 
mal, its  external  form,  how  it  acts  when  alive,  its  external 
and  internal  anatomy  after  death,  and  the  development  of 
other  individuals  of  its  own  species,  the  student  is  then  ready 
to  study  the  classification  of  animals. 

The  best  method  of  studying  classification,  or  Systematic 
Zoology,  is  to  make  an  exhaustive  examination  of  one  an- 


14  ZOOLOGY. 

imal,  and  then  to  study  in  the  same  thorough  manner  an 
allied  form,  and,  finally,  to  compare  the  two.  For  example, 
take  a  frog  and  compare  it  with  a  toad,  and  then  with  a 
newt,  or  a  land  salamander  ;  thus,  by  a  study  of  the  different 
types  of  Batrachians,  one  may  arrive  at  a  knowledge  of  the 
affinities  of  the  different  species  of  the  class.  The  methods 
of  research  are,  then,  observation  and  comparison.  The 
best  and  most  philosophic  observers  are  those  who  compare 
most.  Then,  passing  on  to  other  animals,  the  student  will 
place  in  one  group  animals  that  are  alike.  He  will  find  that 
many  agree  in  certain  general  characters  common  to  all. 
He  will  thus  form  them  into  classes,  and  those  that  agree  in 
less  general  characters  into  orders,  and  so  on  until  those 
agreeing  in  still  less  important  characteristics  maybe  placed 
in  categories  or  groups  termed  families,  genera  and  species, 
varieties  and  races.  For  example,  the  cat  belongs  to  the 
following  groups  : 

Kingdom  of  Animals  ; 

Sub-kingdom,  or  branch,  Vertebrates  ; 
Class,  Mammalia  ; 
Order,  Carnivora  ; 
Family,  Felidae  ; 
Genus,  Felis  ; 

Species,  Felis  domesticus  Linnaeus  ; 
Variety,  Angorensis. 

But  these  different  groups  are  insufficient  to  represent  the 
almost  endless  relationships  and  series  called  the  System  of 
Nature,  which  our  classifications  attempt  to  represent. 
Hence  we  have  sub-species,  sub-genera,  sub-families  and 
super-families,  sub-orders  and  super-orders,  and  sub-classes 
and  super-classes,  and  the  different  assemblages  may  be 
grouped  into  series  of  orders,  families,  etc. 

The  relations  of  the  members  of  these  different  groups 
may  be  represented  in  the  same  manner  as  the  genealogi- 
cal tree  of  the  historian,  or  like  a  tree,  with  its  trunk 
and  branches  and  twigs  ;  or  on  a  plane  by  a  cross-section 
through  the  tree,  the  different  groups  or  ends  of  the 
branches  resembling  a  constellation,  and  embodying  one's 


EIGHT  BRANCHES  OF  THE  ANIMAL  KINGDOM.      15 

idea  of  the  complicated  relations  between  animals  of  differ- 
ent groups. 

The  Animal  Kingdom  may  be  divided  primarily  into 
two  series  of  branches  ;  those  for  the  most  part  composed 
of  a  single  cell,  represented  by  a  single  branch,  the  Proto- 
zoa, and  those  whose  bodies  are  composed  of  many  cells 
(Metazoa),  the  cells  arranged  in  three  fundamental  cell- 
layers — viz.,  the  ectoderm,  mesoderm,  and  endoderm.  The 
series  of  Metazoa  comprises  the  seven  higher  branches — i.e., 
the  Porifera,  Ccelenterata,  Echinodermata,  Vermes,  Mol- 
lusca,  Arthropoda,  and  Vertebrata.  Their  approximate 
relationships  may  be  provisionally  expressed  by  the  follow- 
ing 

TABULAR  VIEW  OF  THE  EIGHT  BRANCHES  otf  THE  ANIMAL  KINGDOM. 


VIII.  Vertebrata. 
Fishes  to  Man. 


VII.  Arthropoda. 
Crustaceans  and  Insects. 


VI.  Mollusca. 
CJams,  Snails,  Cuttles. 


V.  Vermes. 

Flat  and  Round  Worms,  Polyzoa, 
Brachiopods,  Annelids,  Tuuicatea. 


IV.  Echinodermata. 
Crinoids,  Starfish,  etc. 


III.    Ccelenterata. 

Hydra,  Jelly-fishes. 

I 


II.  Porifera. 
Sponges. 


METAZOA. 

Many-celled  animals,  with  3  cell-layers. 

I.  PROTOZOA. 

Single-celled  animals. 


It  should  be  understood  by  the  student  that  the  classifi- 
cation presented  in  this  book  is  a  provisional  one,  based  on 
our  present  knowledge  of  the  structure  of  the  leading  types 


16  ZOOLOGY. 

of  the  animal  kingdom,  and  may  be  regarded  as  rudely  in- 
dicating the  blood-relationship  or  pedigree  of  animals.  It 
differs  in  some  important  respects  from  the  classifications 
given  in  the  books  ordinarily  in  use  by  American  students. 
It  is  a  question  whether  the  Tunicata  should  not  form  a 
ninth  branch,  and  stand  next  below  the  Vertebrates. 

Some  authors  retain  the  four  types  of  Cuvier,  but  it 
should  be  remembered  that  since  Cuvier's  classification  was 
proposed  in  1812  our  knowledge  has  been  greatly  extended. 
The  microscope  has  revealed  an  immense  mass  of  new  mi- 
croscopic forms,  and  many  facts  regarding  the  structure  and 
development  of  the  larger  forms.  The  embranchments  of 
Cuvier  are  in  all  cases,  except  the  Vertebrates,  unwieldy,  het- 
erogeneous, and,  in  the  light  of  our  present  knowledge,  un- 
natural assemblages  of  animals.  New  discoveries  do  away 
with  old  systems,  and  the  classifications  adopted  by  differ- 
ent authors  represent  the  standpoint  from  which  they  re- 
gard the  system  of  nature.  It  is  not  of  so  much  consequence 
to  the  student  to  know  what  the  system  may  be,  as  to  learn 
the  leading  facts  of  animal  morphology  and  development. 

Palaeontology. — With  a  thorough  knowledge  of  the  anat-* 
omy  of  animals  and  their  classification,  the  student  is  pre- 
pared to  study  the  remains  of  extinct  animals,  to  restore  so 
far  as  possible  their  forms,  and  to  classify  them.  With  a 
knowledge  of  the  hard  parts  of  existing  animals,  and  of  the 
interaction  of  the  tendons,  ligaments,  muscles,  and  bones, 
the  palaeontologist  can,  in  accordance  with  the  law  of  cor- 
relation of  parts,  refer  fossils  to  their  respective  orders, 
families,  genera,  or  species. 

Zoogeography,  or  geographical  distribution,  is  the  study 
of  the  laws  of  distribution  of  animals  over  the  surface  of 
the  earth  or  over  the  bottom  of  the  sea.  The  assemblage 
of  animals  inhabiting  any  area  is  called  a  fauna.  Thus  we 
have  an  arctic  fauna,  a  tropical  fauna,  a  North  American 
fauna,  or  Australian  fauna.  The  fauna  of  the  ocean  is  sub- 
divided into  different  subordinate  faunae. 


CHAPTER  I. 

BRANCH    I.— PROTOZOA. 

General  Characters  of  Protozoans. — We  can  imagine  no 
more  elementary  forms  of  life  than  certain  members  of  this 
branch,  whose  bodies  in  the  simplest  forms  are  merely 
masses  of  albumen,  without  any  distinct  permanent  organs, 
or  portions  set  apart  for  the  performance  of  any  special 
function.  Yet  the  primary  acts  of  animal  life,  such  as  tak- 
inJ  food,  its  digestion  and  assimilation,  and  reproduction, 
am  carried  on  as  effectively  by  these  lowest  as  by  the  high- 
^fcforms.  The  simplest  Protozoans  are  like  minute  drops 
<^jprotoplasm  or  albumen,  having  a  gliding  motion,  and 
constantly  changing  their  forms,  throwing  out  temporarily 
root-like  projections  called 
psevdopodia,  which  serve  to 
gather  food-particles.  Fig. 
7  illustrates  a  typical  Proto- 
zoan. It  is  the  common 
Amoeba  of  standing  water. 
Most  Protozoans  are  provid- 
ed with  a  central  organ  or  Fiff.  7.  _Amoeba,  lhc  nnc]eilB  not  8hown. 
nucleus,  which  corresponds 

to  the  reproductive  organs  of  the  many-celled  animals. 
The  Protozoa  are  one-celled  in  distinction  from  all  other 
animals,  from  the  sponges  to  man,  which  are  many-celled, 
though  it  is  claimed  that  a  few  shelled  forms  (Rhizopods)  are 
composed  of  several  indistinct  cells.  Thus  a  Protozoan  cor- 
responds- to  an  egg  or  to  any  one  of  the  cells  composing  the 
bodies  of  higher  animals.  They  may  be  naked,  as  in  Proto- 
mo&ba,  or  Amoeba,  or  may  secrete  a  silicious  or  calcareous 
shell.  The  Infusoria,  forming  the  highest  class,  are  quite 
complicated,  with  permanent  cilia,  a  mouth,  throat,  repro- 


18  ZOOLOGY. 

ductive  nucleus,  and  several  contractile  vesicles,  rudely  an- 
ticipating the  heart  of  higher  animals.  Protozoans  repro- 
duce by  self-division  and  the  formation  of  motile  germs 
(zoospores),  and  in  the  Infusoria  of  ciliated  young.  There 
is  thus  a  great  range  of  forms  leading  from  the  most  primi- 
tive type  (Protamceba)  to  the  most  specialized  forms,  such 
as  the  bell  animalcule  ( Vorticetta.) 


CLASS  I. — MotfERA  (Moners). 

General  Characters  of  Moners. — This  group  comprises 
the  simplest  forms  of  Protozoans,  whence  the  name  Monera 
(novTfpe?,  simple).  The  lowest  forms  are  almost  identical 
in  appearance  with  the  lowest  plants,  and  they  can  only 


Fig.  8.— Protomonas  amyli,  greatly  magnified.  A,  when  encysted;  a*,  germs  or  zo- 
ospores ;  y,  food-mass.  J5,  germ  freed  from  the  parent-cyst.  C,  D,  older  germs.  E, 
adult  encysted  ;  y,  food  ;  «,  projection  inward  of  the  cell-wall ;  x,  wall  of  the  cyst ;  t, 
germs. — After  Cienkowski. 

be  claimed  to  be  animals  from  their  resemblance  to  higher 
forms  leading  to  Amceba,  which,  in  turn,  is  connected  by  a 
series  of  forms  leading  to  undoubted  animals,  such  as  the 
shelled  Rhizopods  (Fig.  14). 

The  Monera  differ  from  the  Rhizopods  (Amoeba,  etc.)  in 
wanting  a  nucleus  and  contractile  vesicles.  Their  body- 
substance  is  homogeneous  throughout,  not  divided  into  a 
tenacious  outer  and  softer  inner  mass,  as  in  Amoeba.  They 
move  by  the  contraction  of  the  body,  and  the  irregular  pro- 
trusion of  portions  of  the  body  forming  either  simple  pro- 
cesses (pseudopodid)  or  a  network  of  gelatinous  threads. 
The  food,  as  some  diatom,  desmid,  or  protozoan,  is  swallowed 


MO  N ERA.  19 

whole,  being  surrounded  and  engulfed  by  the  body,  and  the 
protoplasmic  matter  is  then  absorbed,  serving  for  the  nour- 
ishment and  growth  of  the  Moner. 

The  simplest  form  known,  and  supposed  to  be  really  a  living 
being,  is  HaeckeFs  Protamoeba.  It  may  best  be  described 
by  stating  that  it  is  like  an  Amoeba,  but  without  a  nucleus 
and  vacuoles  (or  little  cavities).  It  reproduces  by  simple 
self -division,  much  as  in  Amceba  (Fig.  11). 

In  Protomonas  the  body  is  very  changeable  in  form,  the 
pseudopods  often  being  very  slender,  thread-like.  Fig.  8, 
A  represents  this  Moner  during  the  formation  of  the  young 
(zoospores)  in  the  cyst-like  body,  or  resting-stage  of  the 
creature  ;  B,  one  of  these  germs  freed  from  the  cyst  and 
capable  of  moving  about  by  the  two  thread-like  pseudopo- 
dia  ;  C  D,  the  Amoeba-like  form  which  the  young  after- 
ward assumes,  and  which  at  maturity  passes  into  the  en- 
cysted or  resting-stage  E. 

A  still  better  idea  of  what  a  Moner  is  may  be  seen  by 
studying  the  Protomyxa  aurantiaca  Haeckel. 

This  Moner  was  discovered  at  the  Canary  Islands.  It  is 
from  half  to  one  millimetre  in  diameter,  and  is  a  perfectly 
simple  mass  of  orange-red  jelly.  When  hungry  numerous 
root-shaped  threads  (pseudopodia)  radiate  from  the  central 
mass.  Fig.  9,  E  represents  the  Protomyxa  after  having 
absorbed  into  its  body-mass  a  number  of  shelled  Infusoria. 
When  about  to  become  encysted  (A  B)  it  rejects  the  shell 
of  its  victims,  retracts  its  false  feet,  and  soon  becomes  fast- 
ened as  minute  red  balls  to  the  surface  of  some  dead  shell. 

The  ball  becomes  enclosed  by  a  thick  covering  (A),  and 
then  the  contents  become  divided  into  several  hundred  small, 
round,  thoroughly  structureless  spheres,  which  become  germs 
(J9).  The  germs  finally  burst  through  the  cyst- wall,  as  in 
C,  «,  c,  d,  and  assume  various  monad-like  and  amoeboid 
shapes,  and  finally  attain,  by  simple  additions  of  the  proto- 
plasm of  its  food  (diatoms  and  infusoria),  the  adult  form 
(D  E}.  Other  Moners  exist  in  fresh  water. 

We  have  been  dealing  with  the  simplest  living  forms,  be- 
ings showing  no  trace  of  organization,  much  lower  and 
simpler  than  the  Amoeba)  with  its  nucleus.  The  individual 


20  ZOOLOGY. 

Moner — for  example,  Protamceba — is  simply  a  speck  or  drop 
of  transparent,  often  colorless,  viscid  fluid,  scarcely  of  more 
consistency  than,  and  in  all  apparent  physical  characters 
identical  with,  the  white  of  a  hen's  egg.  And  yet  this  drop 
of  protoplasm  has  the  power  of  absorbing  the  protoplasm  of 
other  living  beings,  and  thus  of  increasing  in  size — i.e., 
growing  ;  and  in  taking  its  food  makes  various  movements, 
one  or  more  parts  of  its  body  being  more  movable  than 


.  9-Prptomyxa  aurantiaca.    J,  encysted.   B,  cyst  filled  with  germs.    C,  germs 

,  C)   IWniUIE   from    (he    CVSt.       7).    il    vmino-  Pmtnmvvn     enroll™.,;,?^    .,    At~*~:L    ,^ 


,~y*'  uurnmvtca.    A,  encysted.   ±l,  cyst  filled  wit..  ,,_.,.    v,  _C11I10 

(a,  <T  c)  ironing  from  the  cyst.  I),  &  young  Protomyxa  swallowing  a  diatom  (a) 
E,  adult  after  enclosing  or  swallowing  several  shelled  Infusoria.-After  Haeckcl 

others,  the  faculty  of  motion  thus  being  for  the  moment 
specialized  ;  it  has  apparently  the  power  of  selecting  one 
kind  of  food  in  preference  to  another,  and,  finally,  of  repro- 
ducing its  kind  by  a  process  not  only  of  simple  self -division, 
but  also  of  germ-production.  In  short,  we  may  say  of  the 
Moner  what  Foster  says  of  the  Amoeba— viz.,  (1)  it  is  con- 
tractile ;  (2)  it  is  irritable  and  automatic  ;  (3)  it  is  receptive 


MONERA.  21 

and  assimilative  ;  (4)  it  is  metabolic  and  secretory  in  the 
sense  that  the  Moner  digests  and  separates  the  portions 
necessary  for  food  from  those  which  it  rejects  as  waste  ;  (5) 
it  is  respiratory,  the  changes  involved  in  taking  food,  es- 
pecially oxygen,  causing  the  production  of  and  excretion  of 
carbonic  acid  ;  (6)  it  is  reproductive. 

It  is  difficult  to  conceive  of  a  simpler  form  of  life  than 
Protamceba  or  Protomonas.  Are  the  Moners  animals  or 
plants,  or  do  they  represent  a  neutral  division  or  group  of 
forms  ?  It  was  formerly  thought  that  Amoeba  was  the  sim- 
plest possible  form  of  life,  but  we  shall  see  that  that  animal 
is  an  undoubted  organism,  possessing  a  permanent  organ, 
the  nucleus.  Moreover,  the  Amoeba  mtergrades  with  the 
other  Rhizopods  which  are  undoubted  animals,  while  the 
simplest  Monera  have  no  characters  which  absolutely  sepa- 
rate them  on  the  one  hand  from  the  plants  or  on  the  other 
from  the  animals.  Their  relation  to  the  plants  is  seen  in 
the  fact  that,  besides  the  resemblance  to  the  lowest  plants, 
the  cyst  of  Protomonas  is  composed  of  cellulose,  while  the 
granular  contents  of  the  body  become  colored  with  chlo- 
rophyll.* 

For  these  reasons,  Haeckel,  the  discoverer  of  the  Monera, 
regards  them  as  neutral  beings,  neither  plants  nor  animals. 
But  by  comparison  with  other  Protozoa,  we  shall  see  that 
the  Monera  only  differ  from  the  monads  and  Amcebce  by  the 
absence  of  a  nucleus.  This  may  yet  bo  found  to  occur  in 
the  Monera,  and  from  this  fact  we  separate  the  group  only 
provisionally  from  the  Rhizopoda.  The  Gregarincz  also  pass 
through  a  true  Moner- stage.  This  indicates  that  the 
Monera  are  allied  rather  to  animals  than  plants.  Another 
point  of  difference  from  plants  is  the  fact  that,  like  the 
Amoeba,  they  engulf  living  plants  (desmids,  etc.)  and  ani- 
mals (Infusoria),  the  only  plants  known  to  do  this  being  the 
singular  Myxomycetes,  whose  position  is  uncertain,  some 
naturalists  (Allman)  regarding  it  as  an  animal. 

It  is  probable  that  the  Monera  svere  the  earliest  beings  to 

*  On  the  other  hand,  cellulose  occurs  in  the  integument  of  Tunicates, 
and  various  parts  of  Articulates  and  Vertebrates,  while  chlorophyll 
occurs  in  the  Infusoria  and  Hydra. 


22  ZOOLOGY 

appear,  and  that  from  forms  resembling  them  all  other  organ- 
isms have  originated.  We  can  conceive  at  least  of  no  simpler 
ancestral  form;  and  if  organized  beings  were  originally  pro- 
duced from  the  chemical  elements  which  form  protoplasm, 
one  would  be  naturally  led  to  suppose  that  the  earliest  form 
was  like  Protamwba.  It  would  follow  from  this  fact  that  the 
Monera  are  as  low  as  any  plants,  and  that  animals  appeared 
contemporaneously  with  plants. 

Having  studied  a  few  typical  forms  of  Monera,  we  are 
prepared  to  briefly  define  the  group  and  tabulate  the  sub- 
divisions of  the  class. 


CLASS  I.— MONERA  HAECKEL. 

Beings  consisting  of  transparent  protoplasm,  containing  granules,  some- 
times forming  a  net-woi'k,  but  with  no  nucleus*  or  contractile  vacuole  ; 
capable  of  automatically  throwing  out  pseudopodia,  and  reproducing  by 
simple  self-division  of  the  body-mass  into  two  individuals,  or  by  division 
into  a  number  of  germ-like  or  spore-like  young,  which  increase  in  size  by 
absorption  of  Hie  protoplasm  of  other  organisms. 

Group  1 .  Gymnomonera,  comprising  the  genera  Protamceba,  Protogenes, 
and  Myxodictyuin,  which  do  not  become  encysted. 

Gh'oup  2.  Lepomonera,  which  become  encysted  and  protected  by  a 
case,  as  in  the  genera  Protomonas,  Protomyxa,  Vampy- 
rella,  and  Myxastrum. 


CLASS  II. — RHIZOPODA  (Root  Animalcules}. 

General  Characters  of  Rhizopods. — An  idea  of  the  form 
and  internal  structure  of  this  group  can  be  obtained  by  a 
study  of  Amoeba,  which  may  be  found  sliding  over  the  sur- 
face of  the  leaves  of  plants  growing  in  pools  or  ponds  of 
fresh  water.  Our  common  Amoeba  has  been  studied  by 
H.  J.  Clark.  Fig.  10  represents  this  animal  in  the  three 
more  usual  forms  which  it  assumes.  From  time  to  time 
the  sides  of  its  body  project  either  in  the  form  of  simple 
bulgings,  or  suddenly  it  throws  out  foot-like  projections 

*  Should  a  nucleus  be  found  hereafter  to  occur  in  the  Monera,  the 
group  should  be  merged  into  the  Rhizopoda,  and  placed  next  to 
Amoeba. 


RUiZOPODA.  23 

(pseudopodia)  from  various  parts  of  the  body,  as  if  it 
were  falling  apart ;  then  it  retracts  these  transparent  feet 
and  becomes  perfectly  smooth  and  rounded,  resembling  a 
drop  of  slimy,  mucous  mat- 
ter. The  body-mass  is  di- 
vided into  a  clear  cortical  and 
a  medullary,  granular  mass  ; 
the  outer  highly  contractile, 
the  inner  granular  portion 
acting  virtually  as  a  stock  of 

•t      A        rr\\^                        !„-,      vi   ,  Fig.   10. — Amoeba  diffluent*  Ehr.    A,  the 

lOOd.        Ihese     granules,     like  ]eft-hanrt  figure,  the  moat  usmal  form  ;  the 

4-Vin    rrvmi-no  f\f    «V»l/-kvrn-»ViTrll    i-n  right,  shows  the  hroad,  Hat  pseudopodia  ; 

the  grams  OI    CnlOlOpliyll    in  g  anrnw  indicate  the  direction  of  clreula- 

Vegetable     Cells    and    in     dia-  tionof  the  granules.-After  Clark. 

toms  and  desmids,  circulate  in  regular,  fixed  currents,  the 
arrows  in  the  figure  indicating  the  course  of  the  circulating 
food.  The  act  of  circulation  is  probably  assisted  by  a  con- 
tractile vesicle  (or 
vacuole)  usually 
present.  There  is 
besides  a  distinct 
organ  always  pres- 
ent, the  nucleus  (see 
Fig.  11),  so  that  the 
Amoeba  earns  the 
right  to  be  called 
an  organism.  Its 
food  consists  of  one- 
celled  algae,  diatoms, 
desmids,  zoospores, 
and  portions  of  fila- 
mentous algae,  and  it 
possesses  the  power 
of  discrimination  in 

Fig.  11.— Amoeba  spharococcus.    A,  before  division. 

7?,  the  same  in  its  resting  stage;  a,  cyst  or  cell-wall;    taking  ItS  IOOQ.      lllC 
d.  body-mass;    c.   nucleus;    b,   nucleolus.     C,  Amoeba 

TH'nrly  divided.    Z>,  two  young  Amoebae,  the  result  of    AlllO3ba  lias  the  DOW- 
ilivision.— After  Haeckcl.  , 

er  of  moving  m  par- 
ticular directions,  stretching  a  millimetre  in  length  ;  it 
selects  appropriate  food,  and  can  engulf  or  swallow,  digest 
and  distribute  the  food  thus  absorbed  to  various  portions  of 


24  ZOOLOGY. 

its  body.  The  Amoeba  reproduces  its  kind  by  simple  di- 
vision, as  seen  in  Amoeba  splic&rococcus  Haeckel  (Fig.  11). 
This  species,  unlike  others,  so  far  as  known,  becomes  encysted 
(H),  then  breaks  the  cell-wall  and  becomes  free  as  at  A. 
Self-division  then  begins  as  at  C,  the  nucleus  doubling  it- 
self, until  at  D  a  and  D  b  we  have  as  the  result  two  individ- 
uals. 

Order  1.  Foraminifera. — Besides  Amoeba,  several  other 
forms,  either  naked  or  shelled,  produce,  by  division  of  an  in- 
ner portion  of  the  body,  numbers  of  ciliated  young,  as  in 
the  naked  Pelomyxa,  in  certain  many-chambered  Fora- 
minifera, and  in  Collosphce- 
ra.  An  example  may  be 
seen  in  the  European  Pelo- 
myxa palustris  Greef  (Fig. 
12).  This  creature  lives  in 
the  mud  at  the  bottom  of 
fresh-water  pools,  and  when 
first  seen  resembles  little 
dark  balls  of  mud  a  milli- 
metre in  diameter.  Instead 
of  one  nucleus,  there  are 
numbers  of  them,  and  nu- 
merous contractile  vacuoles 

Fig.  12.— Pelomyxa  palustris.    A,  a,  clear  ,,,,    ,       .,,          a    .-,     ,          ,, 

cortical  portion;  b.  diatoms  enclosed  in  the  tilled  With  a  mild,  together 
body-mass.  B,  amcebu-like  bodies  originating  •  ,-t  i  mi 

from  the  nuclei,  which  after  leaving  the  body  With    SplCuleS.       The    JOUHg 

pass  into  monad-like  forms,  0;  n,  nucleus;  .,        Oj.   fl-.-f  om/^Ko  lil™  /  7?^* 

c,  contractile  vesicle. -After  Greef.  &re  at  nrst  amoeba-like  (£>), 

originating     as     "  shining 

bodies,"  which  have  resulted  from  the  self -division  of  the 
nuclei.  These  amoeba-like  bodies  finally  assume  an  active, 
monad-like  stage  C,  and  move  about  by  means  of  a  cilium 
or  lash. 

We  now  come  to  the  shelled  Amoebae,  or  genuine  Forami- 
nifera. A  common  type  is  Arcella,  which  secretes  a  one- 
chambered  silicious  shell,  found  in  fresh  water,  and  a 
representative  of  the  monothalamous,  or  one-chambered, 
Foraminifera;  while  the  many-chambered  forms  are 
marine,  of  which  Globigerina  bulloides  (Fig.  13),  found 
floating  on  the  surface  of  the  ocean,  with  its  pseudopodia 


OF 


Fig.  13.— A  Foraminifer.     Globiyerina  btMoides, 
magnified  70  diameters.— From  Macallister. 


FORAM1NIFERA.  *P 

thrown  out  in  all  directions,  is  a  type  ;  Rot  alia  vcneta  (Fig. 
14)  is  another  example. 

The  Foraminifera  are  nucleated.  Diploplinjs  multiplies 
by  a  "  process  of  con- 
tinuous binary  fis- 
sion." Miliola  gives 
rise  to  small  round, 
sharply  -  defined  bod- 
ies, in  calcareous 
shells,  with  one  turn, 
but  no  inner  walls, 
and  with  pseudopo- 
dia  like  those  of  the 
adult.  Microgromia  so- 
cialis  multiplies  by  zo- 
ospores,  which  are  oval, 
with  two  flagella;  or, 
in  other  cases,  the 
young  assume  an  actinophrys-like  form,  and  move  about  by 
the  aid  of  three  or  four  more  or  less  branched  pointed  pseudo- 
pods  (Her  twig). 
In  some  forms, 
as  the  fossil 
NumnmlUes,  the 
chambers  are 
numerous  and 
regular,  the 
shells  being  flat 
and  consisting 
of  eight  coils  sit- 
uated in  the 
same  plane.  A 
recent  species  ot 
Foraminifer 
found  at  Borneo 
measures  more 

Fig.  14.— Rotalia.    A  Rhizopod,  showing  the  pscudopodia.  nni**a 

Liian  two  incnes 

in  diameter,  while  a  common  form  on  the  Florida  reefs,  de- 
voured in  large  quantities  by  the  Holothuria,  or  sea-cucum- 


26  ZOOLOGY. 

her,  measures  about  one  fifth  of  an  inch  in  diameter.  Most 
of  our  native  species  are  much  more  minute.  The  Eozoon, 
so-called,  is  supposed  by  some  to  be  a  Foraminifer,  but 
others  regard  it  as  more  probably  inorganic,  and  simply  a 


Kg.  15.— s,  OoOotpkara  sjri- 
nosa.  with  projecting  conical 
points,  containing  little  sphe- 
roids, which  pass  into  monad- 
like  bodie*  C.  D,  probahly  an, 
early  stage  of  C.  A,  a  young 
capsule  of  C.  Huxleyi  Miiller.— 
After  Cicnko\\>ki. 


Fig.  16. — Acfinosphcerinm.  «,  a  mor- 
sel of  food  drawn  into  the  cortical  layer 
b;  c,  central  parenchymatous  mass  of 
the  body  ;  d,  some  balls  of  food-stuff  in 
the  latter;  e,  psendopodia  of  the  cortical 
layer.— After  Gegenbaur. 


Fig.  17.—ffeliophrysmriabUi8.  A  sun- 
animalcule,  showing  the  pscudopods, 
nuclei,  and  vacuoles.— From  Macallister. 


mineral.  Undoubted  Foraminifera  occur  in  the  Silurian 
formation,  while  large  masses  of  carboniferous  and  cre- 
taceous rocks  are  formed  by  their  shells. 

Order  2.  Radiolaria. — These  Rhizopods  have  the  general 
structure  of  Amoebae,  but  secrete  beautiful  silicious  shells 


RIIIZOPODA.  27 

of  varied  forms,  more  or  less  spherical,  perforated  for  the 
protrusion  of  the  pseudopodia,  with  often  spicules  or  points 
radiating  from  the  shell.  They  reproduce  apparently  hy 
self -division  of  the  interior,  resulting  in  a  swarm  of  monad- 
like  young.  The  Heliozoa  are  represented  hy  the  fresh- 
water Actinoplirys  sol,  which  is  round,  with  numerous  stiff 
pseudopodia  radiating  in  all  directions  from  the  body,  and 
by  Actinosphaerium  (Fig.  16).  The  true  marine  Radiolaria 
are  represented  by  Collosplmra  spinosa  Cienkowski  (Fig.  15). 
It  possesses  a  perforated  shell  beset  with  small  spines,  which 
encloses  a  capsule  with  a  protoplasmic  wall.  In  the  capsule- 
stage  (A)  it  often  divides  by  fission  into  two  halves.  After- 
ward the  older  capsule  divides  into  a  number  of  little  round 
bodies,  which  develop  two  lashes  as  in  (7. 


CLASS  II.— RHIZOPODA. 

Unicellular  organisms  consisting  of  protoplasm,  with  an  outer  clear, 
cortical,  and  an  inner  granular  mass  containing  one  or  more  nuclei,  and 
one  or  more  contractile  vacuoles ;  moving  by  means  of  pseudopodia,  and 
either  naked  or  secreting  a  one  or  many -chambered  sliell ;  reproducing  by 
self -division,  or  by  the  production  of  several  or  many  amoeboid  or  monad- 


Order.  1.  Foraminifera. — One-celled  Rhizopods  with  one  or  many  nuclei 
and  contractile  vacuoles,  secreting  chambered  calcareous  or 
horny  (chitinous  ?),  rarely  arenaceous,  shells.  (Amoeba, 
Globigerina,  Nummulina.) 

Order  2.  Radiolaria. — Rhizopods  with  pointed,  branched,  usually  anas- 
tomosing and  granular  pseudopodia.  The  body  contains 
either  numerous  small  heterogeneous  nuclei,  or  a  single 
larger,  highly  differentiated  vesicular  nucleus.  The  pro- 
toplasm of  the  body  is  further  separated  into  a  peripheral 
non-nucleated  and  a  central  nucleated  portion  by  a  mem- 
branous capsule  with  porous  walls.  Reproduction  occurs 
by  the  breaking  up  of  the  body  into  monad-like  embryos, 
with  one  or  sometimes  two  locomotive  lashes  (flagella). 
There  are  two  divisions  :  (1) Heliozoa  (Actinophrys,  Actino- 
sphaerium), and  (2)  Radiolaria  (or  Cytophora),  having  as  rep- 
resentatives Acanthometra,  Collozoiim,  Sphaerozoum,  and 
Collosphacra. 


ZOOLOGY. 


CLASS  III.— GREGARINIDA  (Gregarines). 

General  Characters  of  Gregarinida. — The  largest  and 
best  known  species  of  this  group  is  an  inmate  of  the 
intestinal  canal  of  the  European  lobster,  and  was  named 
by  E.  Van  Beneden  Gregarina  gigantea  (Fig.  18).  It 
is  worm-like,  remarkably  slender,  and  is  sixteen  mil. 


Fig.  IS.— Gregarina  giganUa.  L,  two  individuals  of  natural  size.  K,  the  same 
much  enlarged;  n,  nucleus.  A,  the  same  encysted.  B,  subdivision  of  the  cyst.  (7,  divi- 
sion of  the  contents  of  cyst  into  email  spheres,  observed  in  another  species.  JV,  the 
cphcrcs  enlarged.  M.  cyst  filled  with  j>femlor.Hvicelhr,  0.— After  Lieberkuhn.  D—F, 
moncr-likc  young  of  G.  gigantea.  G,  //,  pseadofilaria  stage.  7,  J,  early  nucleated 
forms  of  Gregarina  gigantea.— After  Van  Beneden. 

limetres  (over  half  an  inch)  in  length,  being  the  largest 
one-celled  animal  known.  In  this  organism  an  external, 
structureless,  perfectly  transparent  membrane  with  a  double 
contour  can  be  distinguished.  It  represents  the  cell-wall 
of  the  cells  in  the  higher  animals.  Beneath  this  outer  wall 
is  a  continuous  layer  of  contractile  substance,  forming  a 
true  system  of  muscular  fibrillae  comparable  to  that  of  the 
Infusoria.  The  body-cavity  of  the  Gregarina  contains  a 


OREOAK1NIDA.  29 

viscid  fluid  holding  in  suspension  rounded  granules,  among 
which  the  nucleus  rests.  This  nucleus  contains  an  inner 
vesicle  or  nucleolus,  which  strangely  disappears  and  then 
reappears.  Van  Beneden  distinguishes  three  kinds  of  mo- 
tions in  the  Gregarinae  :  1.  They  represent  a  very  slow 
movement  of  translation,  in  a  straight  line,  and  without  the 
possibility  of  distinguishing  any  contraction  of  the  walls  of 
the  body  which  could  be  considered  as  the  cause  of  the 
movement.  It  seems  impossible  to  account  for  this  kind  of 
motion.  2.  The  next  kind  of  movement  consists  in  the 
lateral  displacement  of  every  part,  taking  place  suddenly 
and  often  very  violently,  from  a  more  or  less  considerable 
part  of  its  body.  Then  the  posterior  part  of  the  body  may 
be  often  seen  to  throw  itself  out  laterally  by  a  brusque  and 
instantaneous  movement,  forming  an  angle  with  the  anterior 
part.  3.  Owing  to  the  contractions  of  the  body,  the  gran- 
ules within  the  body  move  about. 

The  life-history  of  this  Gregarina  is  as  follows  :  It  occurs 
in  its  normal  state  in  lobsters  in  May,  June,  and  August,  but 
in  September  becomes  encysted  in  the  walls  of  the  rectum  of  its 
host,  the  cysts  (Fig.  18,  A)  appearing  like  little  white  grains 
of  the  size  of  the  head  of  a  small  pin.  When  thus  encysted 
the  nucleus  disappears,  and  the  granular  contents  of  the 
cyst  divide  into  two  masses  (J5),  like  the  beginning  of  the 
segmentation  of  the  yolk  of  the  higher  animals.  The  next 
step  is  not  figured  by  Van  Beneden,  and  we  therefore  intro- 
duce some  figures  from  Lieberkuhn  which  show  how  the 
granular  mass  breaks  up  into  spindle-shaped  bodies  (called 
by  some  authors  "  pseudonavicellse,"  and  by  Lieberkuhn 
"  psorosperms")  with  hard  shells.  After  the  disappearance 
of  the  nucleus  and  vesicle,  and  when  the  encysted  portion 
has  become  a  homogeneous  granular  mass,  this  mass  divides 
into  a  number  of  rounded  balls  (Fig.  18,  C).  These  balls 
consist  of  fine  granules,  which  are  the  spindle-shaped  bodies 
in  their  first  stage  (Fig.  18,  N).  They  then  become 
spindle-shaped  (0)  and  fill  the  cyst  (Fig.  18,  M ),  the  balls 
having  meanwhile  disappeared.  From  these  psorosperms 
are  expelled  amoeba-like  ma.sses  of  albumen  (D  E],  which, 
as  Van  Beneden  remarks.,  exactly  resemble  the  Protamwba 


30 


ZOOLOGY. 


already   described.       This    moner-like    being,    without     a 
nucleus,  is  the  young  Gregarina. 

But  soon  the  Amoeba  characters  arise.  The  moner-like 
young  (Fig.  18,  D  E  F)  now  undergoes  a  further  change.  Its 
outer  portion  becomes  a  thick  layer  of  a  brilliant,  perfectly 
homogeneous  protoplasm,  entirely  free  from  granules,  which 
surrounds  the  central  granular  contents  of  the  cytode 
(Haeckel)  or  non-nucleated  cell.  This  is  the  Amoeba  stage 
of  the  young  Gregarina,  the  body,  as  in  the  Amoeba,  con- 
sisting of  a  clear,  cortical,  and  granular 
medullary  or  central  portion. 

The  next  step  is  the  appearance  of  two 
arm-like  projections  (Fig.  18,  F),  com- 
parable to  the  pseudopods  of  an  Amoeba. 
One  of  these  arms  elongates,  and,  sepa- 
rating, forms  a  perfect  Gregarina.  Soon 
afterward  the  other  arm  elongates,  ab- 
sorbs the  moner-like  mass,  and  also  be- 
comes a  perfect  Gregarina.  This  elon- 
gated stage  is  called  a  Pseudofilaria  (Fig. 
18,  G)  •  no  nucleus  has  yet  appeared. 
In  the  next  stage  (Fig.  18,  If  n,  nucleus) 
the  body  is  shorter  and  broader,  and  the 
nucleus  appears,  while  a  number  of  gran- 
ules collect  at  one  end,  indicating  a 
head.  After  this  the  body  shortens  a 
little  more  (/,  J),  and  then  attains  the 
elongated,  worm-like  form  of  the  adult 
Gregarina  (1C).  Van  Beneden  thus  sums  up  the  phases  of 
growth  : 

1.  The  Moner  phase. 

2.  The  generating  Cytode  phase. 

3.  The  Pseudofilaria  phase. 

4.  The  Protoplast  (adult  Gregarina). 

5.  The  encysted  Gregarina. 

6.  The  sporogony  phase  (producing  zoospores). 

The  Gregarinae  and  Amoeba  constitute  HaeckePs  group 


beetle, 
sum.  1, 
with  a  beak-like  continua- 
tion (a')  of  the  head.  2, 
older;  a,  anterior  end;  6, 
hinder  part  of  thejbody; 
c,  nucleus. — After 
baur. 


THE  INFU80R1ANS.  31 

of  Protoplasta.  Other  Gregarinae  are  very  minute,  and  are 
parasitic  in  insects  (Fig.  19),  etc.,  and  vary  greatly  in  form, 
some  being  apparently  segmented,  while  in  a  few  forms  the 
body  ends  anteriorly  in  a  sort  of  beak  armed  with  recurved 
horny  spines.  We  are  now  prepared  to  adopt  the  following 
definition  of  the  class  : 


CLASS  III.— GREGARINIDA. 

Amoeba-like  Protozoa,  more  or  less  elongated,  with  a  determinate  cell- 
watt,  with  a  subcuticular  system  of  muscular  fibrillce,  with  a  nucleus,  but  no 
contractile  vacuole  ;  reproducing  by  encysting  and  subdivision  of  the  cen- 
tral mass  of  Hie  body,  producing  shelly  psorosperms,  from  which  escape  the 
moner-like  young,  which  undergo  a  metamorpJwsis  into  the  usually  worm- 
shaped,  parasitic  adult  (Gregarina). 


CLASS  IV. — INFUSORIA. 

These  organisms  can  best  be  understood  by  studying  rep- 
resentatives of  the  three  orders  forming  the  class. 

Order  1.  Flagellata  (Monads). — A  familiar  example  of 
monads,  Nonas  termo  Ehrenberg?  has  been  studied  by 
H.  J.  Clark.  His  description  will  suit  our  purpose  of  indi- 
cating the  form  and  habits  of  a  typical  flagellate  animalcule. 
It  somewhat  resembles  our  figure  of  Uvella  in  its  general 
shape,  being  pear-shaped,  faint  olive  in  color,  and  provided 
with  a  vibratile  locomotive  lash  or  flagellum.  In  swimming, 
the  monad  stretches  out  the  flagellum,  which  vibrates  with 
an  undulating,  whirling  motion,  and  produces  a  peculiar 
graceful  rolling  motion.  When  the  monad  is  fixed  the  fla- 
gellum is  used  to  convey  food  to  the  mouth,  which  lies  be- 
tween the  base  of  the  flagellum  and  beak,  or  "  lip."  The 
food  is  thrown  by  a  sudden  jerk,  and  with  precision,  directly 
against  the  mouth.  "  If  acceptable  for  food,  the  flagellum 
presses  its  base  down  upon  the  morsel,  and  at  the  same  time 
the  lip  is  thrown  back  so  as  to  disclose  the  mouth,  and  then 
bent  over  the  particle  as  it  sinks  into  the  latter.  When  the 
lip  has  obtained  a  fair  hold  upon  the  food,  the  flagellum 
withdraws  from  its  incumbent  position  and  returns  to  its 
former  rigid,  watchful  condition.  The  process  of  degluti- 


32  ZOOLOO  T. 

tion  is  then  carried  on  by  the  help  of  the  lip  alone,  which 

expands  latterly  until  it 
completely  overlies  the 
particle.  All  this  is  done 
quite  rapidly,  in  a  few  sec- 
onds, and  then  the  food 
glides  quickly  into  the 
depths  of  the  body,  and  is 
enveloped  in  a  digestive 

Fig.20.-Monad8(Cr^a).-AfterTuttle.       yacuole?  whilst  the  lip  ES- 

sumes  its  usual  conical  shape  and  proportions. "  (Clark.) 
All  the  monads  have  a  contractile  vesicle.  In  Monas 
termo,  Clark  observes  that  it  is  "  so  large 
and  conspicuous  that  its  globular  form 
may  be  readily  seen,  even  through  the 
greatest  diameter  of  the  body ;  and  con- 
tracts so  vigorously  and  abruptly,  at  the 
rate  of  six  times  a  minute,  that  there 
seems  to  be  a  quite  sensible  shock  over 
that  side  of  the  body  in  which  it  is  em- 
bedded." The  contractile  vesicle  is 
thought  to  represent  the  heart  of  the 
higher  animals.  The  reproductive  organ 
may  possibly  be  represented  in  Monas 
termo  by  a  "very  conspicuous,  bright, 
highly  refracting,  colorless  oil-like  globule 
which  is  enclosed  in  a  clear  vesicle"  called 
the  nucleus.  This  and  other  monads  live 
either  free  or  attached  by  a  slender  stalk. 
As  an  example  of  the  compound  or  aggre- 
gated monads  may  be  cited  Uvella,  prob- 
ably glaucoma  of  Ehrenberg.  Other 
forms,  as  Codosiga,  are  fixed  by  a  stalk  to, 
some  object  (Fig.  21,  C.  pulclierrimus 

™      1  -v       T     J.T  •          j     n-    i   •  Flg-  21.—  A,  Codostqa 

Clark).    In  this  and  allied  forms  the  body,  putilUrrimw.     B,  the 


is  surmounted  by  a  collar  or  calyx  out 

which  the  flagellum  projects.     The   Qo:- 

dosiga  has  been  observed  by  Clark  to.uii-  als-"Afte;r  Clark- 

dergo  fission,  two  independent  monads  resulting,  within  the 

space  of  forty  minutes. 


THE  FLAGELLATE  INFUSORIA. 


33 


The  first  sign  of  fission  is  a  bulging  out  of  the  collar, 
which  becomes  still  more  bell-shaped.  The  flagellum  next 
disappears.  Then  marks  of  self-division  appear  in  a  nar- 
row, slight  furrow  (Fig.  21,  B,  e),  extending  from  the  front 
half  way  back  along  the  middle  of  the  body.  Meanwhile 
the  collar,  which  had  become  conical,  expands,  and,  most 
striking  change  of  all,  two  new  flagella  appear.  Then  the 
collar  splits  into  two  (Fig.  21,  C),  and  soon  the  two  new  Codo- 
sigge  become  perfected,  when  they  split  asunder,  and  become 
like  the  original  Codosiga.  Such  is  the  usual  mode  of  mul- 
tiplication of  the  species  in  the  monads. 

A  few  monads  have  been  observed  to  become  encysted,  and 
to  break  up  into  excessively  minute  bodies,  from  which  new 
monads  have  grown.  Two 
individuals  of  the  same  form 
(Heteromita)  in  certain  stages 
fasten  themselves  together, 
the  larger  absorbing  the 
smaller  as  if  conjugating, 
like  Desmids,  the  compound 
body  resulting  becoming  en- 
cysted ;  finally  the  contents 
of  the  cyst  become  divided 
into  either 

which 

sume  the  parent  form.  The  researches  of  Messrs.  Dallinger 
and  Drysdale  on  this  Heteromita  have  proved  that  while 
the  mature  forms  may  be  destroyed  at  a  temperature  of 
142°  F. ,  the  motile  germs  of  this  and  five  other  species  of  Infu- 
soria perished  when  heated  in  fluid  to  from  212°  F.  to  268°  F. 

Noctiluca  (Fig.  22)  has  been  proved  by  Cienkowski  to  be 
an  enormous  monad.  It  is  a  highly  phosphorescent  organ- 
ism, so  small  as  scarcely  to  be  seen  with  the  naked  eye,  be- 
ing from  £  to  1  mm.  (-01  to  *04  inch)  in  diameter.  It  occurs 
in  great  numbers  on  the  surface  of  the  sea.  It  has  a  nearly 
spherical  jelly-like  body,  with  a  groove  on  one  side  from 
which  issues  a  curved  filament,  used  in  locomotion.  Near 
the  base  of  this  filament  is  the  mouth,  having  on  one  side  a 
tooth-like  projection.  Connecting  with  the  mouth  is  an  oes- 


Fig.  22.—  Noctiluca  miliaris,  after  Hux- 

large    Or    minute  ley,  and  its  zoospores.    s,  style  j  n,  nuclc- 
gerniS    (zOOSpOres)     which    as-  U8<   ^eatly  magnified.-Aftcr  Cienkowski. 


34  ZOOLOGY. 

ophagus  which  passes  into  the  digestive  cavity,  in  front  of 
which  lies  an  oval  nucleus.  Beneath  the  outer  skin  or  firm 
membrane  surrounding  the  body  is  a  gelatinous  layer,  con- 
taining numerous  granules.  A  network  of  granular  fibres 
arises  from  the  granular  layer  ;  these  fibres  pass  into  the 
middle  of  the  body  to  the  nucleus  and  digestive  cavity.  The 
young  (Fig.  22,  n,  s)  result  from  a  division  or  segmentation 
of  the  entire  mass  of  the  protoplasm  of  the  body,  forming 
small  oval  bodies  with  a  long  lash.  The  zoospores  are  like 
those  of  other  Flagellata,  and  for  this  reason  and  the  gen- 
eral structure  of  the  adult,  Noctiluca  is  by  the  best  author- 
ities associated  with  the  Flagellata.  Noctiluca  also  under- 
goes conjugation,  but  the  zoospores 
appear  whether  conjugation  has  oc- 
curred or  not.  The  Noctiluca  on  the 
coast  of  the  United  States  has  been 
observed  in  abundance  on  the  surface 
of  the  sea  in  Portland  harbor,  by  Mr. 
E.  Bicknell.  It  is  phosphorescent, 
but  whether  identical  with  Noctiluca 
miliaris  of  the  European  seas  is  not 
known.  Leptodiscus  medusoides  Hert- 
wig,  is  discoidal  or  medusiform  in 

Fi%.23.—Actnetamystactna,     _  °          ,1-1-1  -IT 

with  its  stalk  attached  to  a  shape,  the  disk  one  ana  a  halt  milli- 

plant ;  with  fifteen  tentacles  .       , .  TT..,  ., .    .       ,      , 

ending  in  knob-like  expan-  metres  in  diameter.     When  disturbed 

sions  or  puckers.—  From  Mac-   -111,1  1,1  i        11 

aiiister.  it  darts  through  the  water  by  the  con- 

tractions of  its  umbrella-shaped  body. 
It  is  allied  to  Noctiluca  and  was  discovered  at  Messina. 

Peridinium  is  the  type  of  a  third  and  higher  division  of 
monads,  the  body  being  protected  by  a  hard  shell,  with  one 
or  more  flagella,  and  a  row  of  cilia  serving  as  a  locomotive 
apparatus,  and  thus,  together  with  Heteromastix  and  Dys- 
teria,  connecting  the  Flagellata  with  the  Ciliata  or  true 
Infusoria. 

Order  2.  Tentaculifera  (Acinetae,  Suctoria), — An  Acineta 
(Fig.  23)  reminds  us  at  first  sight  of  a  Radiolarian,  since 
the  body  is  provided  with  filiform,  tentacle-like  processes 
resembling  the  pseudopodia  of  a  Radiolarian,  but  the  ten- 
tacles are  in  reality  rather  stiff,  hollow,  and  act  as  suck- 


THE  GILIATE  INFUSORIA. 


35 


ers,  so  that  when  the  organism  lias  by  means  of  its  hollow 
arms  or  tentacles  caught  some 
Infusorian,  the  arms  con- 
tract, draw  the  victim  nearer 
to  the  Acineta,  and  when  the 
sucking  disk  at  the  end  of  the 
arms  has  penetrated  the  skin, 
the  contents  of  the  body  of 
the  Infusorian  are  sucked  into 
the  food-cavity  of  the  Acine- 
ta ;  on  the  other  hand,  in 
some  Acinetee  a  portion  of  the 
arms  are  simply  prehensile. 
These  animals  are  in  their 
adult  phase  quite  unlike  the 
Flagellata  or  Ciliata,  but  the 
young  are  developed  within 
the  parent  and  are  provided 
with  cilia,  being  at  first  free- 
swimming,  and  afterward 
fixed  by  a  long  stalk.  The 
Ac  i  net  (B  sometimes  self -di- 
vide, sending  off  from  the 
free  end  of  the  body  a  ciliated 
Acinete  ;  they  have  also  been 
seen  to  conjugate. 

Order  3.  Ciliata  (Infuso- 
ria).— A  common  type  of  this 
group  and  one  easy  to  obtain 
by  the  student  is  Parame- 
cium (Fig.  24),  observed  in 
infusions,  or  moving  rapidlv 

,  -i       -i      -i  •  »  -,  .        Fig.   24. — Paramecium   caudatum,     A 

OVer  the  bodies  Of   larger  am-  view  from  the  dorsal  side,  magnified  340 

mals  which  may  be  under  the  diameter«-  *  the  hea(1:  ^  the  tai1' 


the  mouth;  m  to  g,  the  throat;  a,  the  pos- 
terior opening  of  the  digestive  cavity;  cpl 
the  anterior  and  cv  posterior  contractile 


microscope.     Figure  24  rep- 
resents  Paramecium   cauda-  wl;  n  the  reproductivc  organ 

tum    Ehreilberg.        This    aili-  iTO  vibrating^ilia  at  the  edge  of  the  ves- 

malcule  is  a  mass  of 


is  a  mass  of   proto- 
plasm, representing  a  single  cell. 


tibule.— After  H.  J.  Clark. 


In  the  body-mass  are  ex- 


36 


ZOOLOO  Y. 


cavated  a  mouth  and  a  throat  leading  to  a  so-called  stomach 
or  digestive  cavity.  Two  hollows  in  the  body  form  the  con- 
tractile vesicles,  and  an- 
other cavity  constitutes 
the  reproductive  organ. 
Prolongations  of  the  body- 
mass  form  the  cilia,  which 
characterize  the  Infusoria 
and  give  the  name  to  the 
present  order,  Ciliata. 
Paramecium  has  an  elon- 
gated, oval  body  "with 
one  end  (H )  flattened  out 
broader  than  the  other, 
and  twisted  about  one 
third  way  round,  so  that 
the  flattened  part  resem- 
bles a  very  long  figure  8." 
In  this  form,  as  well  as  in 
Stentor  (Fig.  25),  as  Clark 
remarks,  "  we  have  the 
mouth  at  the  bottom  of  a 
broad  notch  or  incurva- 
tion, and  the  contractile 
vesicle  on  the  opposite 
side,  next  the  convex 
magnified  130  back,  whilst  the  general 
body  lies  be- 
two." 


sh 


Fig.  25.— 


diameters,  expanded  and  bent  slightly  over  to-  p  -^  nf 
ward  the  observer;  the  mouth  m,  next  the  eye,  CaVlt}  OI 
and  the  dorsal  edge  in  the  distance.  «,  poste-  x  +V»P«P 

rior  end;  sh,  the  tube  encl  -  ^Ween    inefee 

ated  border  of  the  disk  (s) 


TViP 


.       , 
rior  end;  sh,  the  tube  enclosing  a  ;  c,  the  cili- 

);  v,  the  larger  rigid  qrvnw3  in  flip  ficrnrp  rpnrp 
cilia;  c»,  the  contractile  vesicle  in  the  extreme  ariows 


distance,seen  through  the  whole  thickness  of  the  opnf  thp  rnnrsp  of  thp  rtftr- 

body;  c?»,c»a,  the  posterior  prolongation  of  c»,  SenL  inG 

in  the  distance;  r,r«,  the  circular  and  radiating  tides  of  indigo  with  which 

branches  of  what,  by  Clark,  was  supposed  to  be  ° 

a  rudimentary  nervous  system;  n,  nl.  the  re-  Clark    fed     lllS    Specimens, 

productive  system,  extending  from  the  right  i  •   i     i 

side,  at  n,  posteriorly,  but  toward  the  eye  at  nl.  as      tllCV      are       Whirled 

—After  Clark.  J..                        ., 

along,  by  the  large  vibrat- 

ing cilia  (v)  of  the  edge  of  the  disk,  against  the  vestibule  of 
the  mouth."  During  the  circuit  the  food  is  digested,  a 
mass  of  rejectamenta  is  formed  near  the  protuberance,  a, 
which  has  appeared  a  short  time  before.  This  finally 


THE  VILIATE  INFUSORIA. 


37 


opens,  allows  the  rejected  matter  to  pass  out,  and  then 
closes  over,  leaving  no  trace  of  an  outlet.  This  and  other 
Infusoria  seem,  then,  to  have  a  definite  digestive  tract,  hol- 
lowed out  of  the  parenchyma  of  the  body. 

"  The  system,"  says  Clark,  "  which  is  analogous  to  the 
blood-circulation  of  the  higher  animals,  is  represented  in 
Paramecium  by  two  contractile  vesicles  (cv,  cvl,  i,  n,  in), 
both  of  which  have  a  degree  of  complication  which,  per- 
haps, exceeds  that  of  any  other  similar  organ"  in  these  ani- 
mals. When  fully  expanded  they  appear  round,  as  at  c  v  ; 
but  when  contracted  they  appear,  observes  Clark,  as  "  fine 
radiating  streaks,  and  as  the  main  portion  lessens  they  grad- 
ually broaden  and  swell  until  the  former  is  emptied  and 
nearly  invisible,  and 
they  are  extended 
over  half  the  length 
of  the  body.  In  this 
condition  they  might 
be  compared  to  the 
arterial  vessels  of  the 
more  elevated  classes 
of  animals,  but  they 
would  at  the  same 
time  represent  the 
veins,  since  they 
serve  at  the  next  moment  to  return  the  fluid  to  the  main 
reservoir  again,  which  is  effected  in  this  very  remarkable 
way."  The  contents  of  these  vesicles  is  a  clear  fluid. 

The  reproductive  organ  in  Paramecium  is  a  small  tube 
(ri),  only  seen  at  the  reproductive  period  when  the  eggs  (ri) 
are  fully  grown.  Clark  says  that  the  eggs  are  arranged  in 
it  "  in  a  single  line,  one  after  the  other,  at  varying  dis- 
tances." It  usually  lies  in  the  midst  of  the  body,  and  ex- 
tends from  one  half  to  two  thirds  of  the  length  of  the  ani- 
mal. The  eggs  pass  out  from  the  so-called  ovary  through 
an  aperture  near  the  mouth.  Lasso-cells  like  those  in  the 
jelly-fishes  are  said  by  Butschli  to  exist  in  an  infusorian 
named  by  him  Polykrikos. 

In  the   trumpet   animalcule  (Fig.  25,  Stentor  polymor- 


Fig.  £6  — Process  of  fission  in  Stentor  jwlymorphits. 
b,  a  new  Stentor  budding  out;  e,  ready  to  separate  from 
the  original  one;  f.  the  two  in  a  contracted  state. — 
After  Cox. 


38  ZOOLOGY. 

pirns  Ehrenberg)  we  have  a  rather  more  complicated  form, 
the  infusorian  attaching  itself  at  one  end  by  a  stalk,  and 
building  up  a  slight  tube,  into  which  it  contracts  when  dis- 
turbed. The  Stentor  may  be  sometimes  observed  multiply- 
ing by  self-division.  Clark  observed  Stentor  polymorplms 
undergoing  the  process.  The  first  change  observed  was  the 
division  of  the  contractile  vesicle  into  two.  The  mouth  of 
the  new  Stentor  was  formed  in  the  middle  of  the  under  side, 


Pig.  Zf.—EpistylisJlavicans  Ehr.,  a  single,  many-forked  colony  of  bell  animalcules, 
slightly  magnified.  Pig.  28,  one  of  the  animalcules  magnified  250  diameters,  p,  the 
stem;  rf,  the  flat  spiral  of  vibrating  cilia  at  the  edge  of  the  disk;  ms,  the  muscle;  m  to 
6.  the  depth  of  the  digestive  cavity  ;  m,  the  mouth  ;  y,  gl,  the  throat,  or  rudimentary 
digestive  canal ;  cvt  the  contractile  vesicle  ;  /*,  the  reproductive  organ  or  nucleus.— 
After  Clark. 


first  appearing  as  a  shallow  pit,  around  which  arises  a  semi- 
circle of  vibratile  cilia.  The  mouth  and  throat  form  in  the 
new  Stentor  before  any  signs  of  division  appear,  but  in  the 
course  of  two  hours  the  body  splits  asunder,  and  two  new  in- 
dividuals appear.  Fig.  26  illustrates  the  mode  of  self- 
division  seen  in  Stentor  polymorplms  Ehrenberg,  by  Hon. 
J.  D.  Cox.  The  process  in  this  occupied  two  hours  ;  at  the 
final  stage  (Fig.  26,  /)  the  connection  between  the  two  ani- 
malcules parted,  "  and  the  two  Stentors  swam  separately 


THE  CIL1ATE  INFUSORIA.  39 

away,  both  assuming  the  common  form  of  the  animalcule 
when  free-swimming,  and  differing  from  the  original  indi- 
vidual only  in  being  of  smaller  size." 

The  most  complicated  as  well  as  most  interesting  form  of 
all  the  Infusoria  is  the  bell-animalcule,  VorticeUa.  It  is 
very  common  in  pools,  forming  patches  like  white  mould  on 
the  leaves  and  stems  of  submerged  plants.  It  may,  like 
Stentor,  be  observed  under  low  powers  of  the  microscope. 
Their  motions,  as  they  suddenly  contract  and  then  shoot 
out  their  bell,  mounted  on  a  long  stalk,  are  very  interesting. 
The  throat  (oesophagus)  is  quite  distinct,  while  the  nucleus 
is  the  most  conspicuous  organ  of  the  body.  The  digestive 
cavity  is  a  large  hollow  in  the  protoplasm  forming  the  body- 
mass,  in  which  the  whole  mass  of  food  revolves  in  a  deter- 
minate channel.  Closely  allied  to  VorticeUa  is  Epistylis 
(Figs.  27  and  28). 

While  most  ciliate  Infusoria,  so  far  as  known,  multiply 
by  self-division,  in  Vaginicola  the  process  is  more  like  true 
gemmation  or  budding,  and  is  accompanied  by  a  process  of 
encysting,  resulting  in  the  production  of  a  free-swimming 
ciliated  embryo,  the  adult  Vaginicola  being  attached.  The 
VorticeUa  also  becomes  encysted,  and  the  nucleus  subdivides 
until  the  body  becomes  filled  with  monad-like  germs,  the 
result  of  the  simultaneous  breaking  up  of  the  nucleus.  The 
VorticellcB,  then,  pass  through  a  flagellate  or  monad  stage, 
from  which  they  pass  into  the  VorticeUa  condition,  when 
they  multiply  by  self-division  and  by  budding,,  the  last 
generation  becoming  encysted. 

Conjugation  is  a  common  occurrence  in  ciliate  Infusoria, 
and  results  in  the  breaking  up  of  the  nucleus  of  each  indi- 
vidual into  a  number  of  fragments,  and  the  appearance  in 
each  of  the  individuals  of  the  nucleus  and  nucleolus  (either 
single  or  multiple)  which  characterize  the  species.* 

*  Balbiani  believes  that  the  ciliate  Infusoria  have  eggs  which  are 
fertilized  by  spermatic  particles.  More  recently,  however,  Engelmann, 
Biitschli,  and  Hertwig  have  denied  that  conjugation  is  of  a  truly  sexual 
character,  and  that  the  striated  nucleoli  of  certain  individual  Infusoria 
are  spermatozoa.  "  Nevertheless,"  remarks  Huxley  (Anatomy  of  In- 


1 

40  I 


ZOOLOGY. 


CLASS  IV.  —  INFUSORIA. 


Flagellate  or  ciliate  (sometimes  only  ciliate  in  the  early  stages)  Protozoa, 
the  body  not  changing  in  f  own,  having  a  definite  skin,  and  often  wholly  or 
partly  provided  with  cilia;  usually  free,  .  metimes  stalked  or  attached;  with 
a  moutli-opening  and  wsopfiagus,  and  rudiments  of  digestive,  circula- 
tory (two  or  more  contractile  vesicles),  and  reproductive  organs  (nucleus  and 
nudedus),  but  with  no  distinctively  sexv  il  organs. 

Order  1.  Flagettata.  —  Rounded,  oval,  or  pear-shaped  organisms,  usually 
exceedingly  minute,  provided  with  one  or  two  flagella,  with 
an  oral  region,  into  which  particles  of  food  are  thrown  by 
the  flagellum  ;  with  a  nucleus  and  contractile  vesicles,  rarely 
stalked,  and  with  a  calyx;  sometimes  aggregated;  with  a  row 
of  cilia  in  the  highest  forms  serving  as  a  locomotive  appara- 
tus ;  reproducing  by  self  -division  or  by  segmentation  of  the 
protoplasmic  contents  of  the  body,  the  young  being  minute 
oval  bodies,  provided  with  a  flagellum  (Monas,  Heteromita, 
Noctiluca,  Peridinium). 

Order  2.  Tentaculifera  (Suctoria).  —  Naked,  not  ciliated,  protozoans, 
with  long,  stiff,  retractile  arms  or  tentacles,  provided  with  a 
sucker  at  the  end,  the  arms  hollow,  conveying  the  food  to 
the  digestive  cavity  ;  originating  from  ciliated  young  ;  also 
by  self  -division  throwing  off  ciliated  forms,  and  undergoing 
conjugation  (Acineta). 

Order  3.  Ottiata  (True  Infusoria).  —  Body  free  and  covered  with  cilia 
(Paramecium,  Stentor,  etc.),  or  stalked,  with  the  cilia  con- 
fined to  the  head  end  (Vaginicola  and  Vorticella,  etc.)  ;  a 
well-defined  mouth  and  oesophagus  ;  a  digestive  cavity  and 
vent  ;  a  large  nucleus,  and  two  or  more  contractile  vesicles. 
Reproducing  by  self  -division,  budding  or  conjugating,  and 
producing  monad-like  young  by  self-division  of  the  nu- 
cleus ;  sexuality  doubtfully  indicated. 

The  following  diagram  represents  the  relative  position 
of  the  orders  and  classes  of  Protozoa,  and  in  a  rude  way 
their  possible  genetic  relations  : 

vertebrated  Animals,  p.  662),  "  it  is  still  possible  that  the  conjugation 
of  the  Infusoria  may  be  a  true  sexual  process,  and  that  a  portion  of  the 
divided  endoplastules  [striated  nucleoli]  of  each  may  play  the  part  of 
the  spermatic  corpuscle,  the  conjugation  of  which  with  the  nucleus  of 
the  ovum  appears,  from  recent  researches,  to  constitute  the  essence 
of  the  act  of  impiegnation." 


CLASSIFICATION  OF  PROTOZOA. 


41 


VIEW  OF  THE  CLASSIFICATION  OF  THE  PROTOZOA. 


Ciliata. 
(Paramecium.) 


Ten1  'culata. 
(A  Ineta.) 

1 


FlageUata. 
(Monas.) 


! 
INFUSORIA. 


Radiolaria. 
(Actinophrye.) 


GREGARINIDA. 
1 

Foraminifera. 
(Rotalia.) 

RHIZOPODA. 

I 

MONERA. 

Laboratory  Work. — None  of  the  Protozoa,  except  the  shells  of  the 
Foraminifera  and  Radiolaria,  can  be  well  preserved  after  death,  and  it 
is  always  better  to  study  any  animal  alive  or  freshly  killed  than  when 
preserved  in  any  sort  of  fluid.  Fresh-water  Amcebce  and  Monera 
should  be  looked  for  on  the  surface  of  leaves  and  the  stems  of  sub- 
merged plants  in  ponds,  pools,  and  ditches.  Many  fresh-water  Rhizo- 
pods  dwell  in  sphagnum  swamps  and  in  damp  moss  or  in  shaded  pools. 
The  marine  forms  may  be  gathered  with  a  fine  towing  net,  when  the 
surface  of  the  ocean  is  calm.  The  commoner  Foraminifera  will  be  found 
on  shells  and  stones  at  low- water  mark  or  in  shallow  water,  but  most 
abundantly  at  greater  depths — i.  e. ,  from  ten  to  one  hundred  fathoms. 
On  being  placed  in  water  they  will,  after  a  period  of  rest,  send  out 
their  pseudopodia. 

To  study  their  form  and  development  they  should  be  placed  in  a 
drop  of  water  in  an  animalcule  or  aquatic  box,  and  kept  in  this  way 
for  several  days  and  even  weeks,  the  box  being  examined  daily,  and 
water  added  if  necessary.  The  shells  may  be  studied  by  grinding  and 
slicing  into  transverse  and  longitudinal  sections.  The  animals  of 
Miliola  and  other  forms  (Rotalia,,  Textillaria),  on  being  treated  with 
diluted  chromic  acid  and  stained  with  carmine,  disclosed  to  Hertwig  a 
well-marked  nucleus.  The  nucleus  may  also  be  deeply  stained  by 
haematoxylin  or  carmine,  and  may  be  clearly  demonstrated  by  acetic 
acid,  which  tends  to  destroy  the  surrounding  protoplasm.  Much  in- 
genuity, mechanical  skill,  and  patience  is  required  in  the  study  of  the 
Protozoa,  and  much  yet  is  to  be  learned  regarding  their  mode  of  de- 
velopment and  their  structure. 


CHAPTER  II. 

BRANCH  II.—  PORIFERA  (SPONGES). 

General  Characters  of  Sponges. — Although  the  sponges 
were  formerly  supposed  to  be  compound  or  social  Amoebae, 
and  more  recently  monads,  from  the  striking  resemblance 
of  their  epithelial  cells  to  certain  monads,  and  have  been 
generally  regarded  as  Protozoans,  later  researches  have 
shown  that  they  are  in  reality  many-celled  animals,  and  that 
for  a  short  period  of  their  life  they  follow  the  same  develop- 
mental path  as  the  higher  animals.  It  was  also  discovered 
that  they  reproduce  by  eggs,  the  latter  undergoing  segmen- 
tation and  assuming  the  condition  of  a  three-layered  sac, 
the  three  layers  being  identical  with  those  of  the  higher 
branches  of  the  animal  kingdom,  so  that  the  gap  between 
the  Protozoans  and  sponges  is  a  wide  one,  and  the  latter  are 
more  nearly  allied  to  the  Hydra,  for  example,  than  to  any 
one-celled  animal. 

One  of  the  simplest  sponges,  such  as  Ascetta  primordialis 
Haeckel,  is  a  spindle  or  vase-shaped  cylinder,  attached  by  its 
base,  with  the  cellular  soft  portion  supported  by  a  basket- 
work  of  interlaced  needles  or  spicules  of  silex  or  lime.  The 
cells  are  arranged  in  three  layers,  the  innermost  (endoderm) 
being  provided  each  with  a  cilium.  The  spicules,  and  also 
the  eggs,  are  developed  in  the  middle  layer  (mesoderm). 
Moreover,  the  walls  of  the  body  are  perforated  by  multitudes 
of  small  pores  (whence  the  name  of  the  branch,  Porifera), 
through  which  the  water  percolates  into  the  body-cavity, 
carrying  minute  forms  of  life  or  food-particles,  which  are 
individually  thrown  into  each  cell  by  the  action  of  the  single 
cilium  thrust  out  of  the  collar  of  the  cell,  much  as  in  an  in- 
dividual monad  such  as  Codosiya  (Fig.  21).  Each  cell  re- 


STRUCTURE  OF  8PONGES.  43 

jects  its  own  waste  particle  of  food,  the  protoplasm  having 
been  previously  absorbed,  and  the  waste  from  all  the  epi- 
thelial cells  is  collectively  expelled  from  the  single  excurrent 
orifice  (osculurn),  there  being  many  pores  or  mouths,  and 
but  a  single  outlet  for  the  rejectamenta. 

Such  is  the  structure  of  one  of  the  simplest  sponges  ;  the 
larger  common  sponges  differ  mainly  in  having  a  less  defi- 
nite form,  with  numerous  sacs  or  digestive  cavities  or  cham- 
bers, and  numerous  excurrent  orifices  or  oscula.  It  will  be 
seen,  then,  that  we  have  in  the  sponge  a  three-layered  ^§Cj 
its  cavity  rudely  foreshadowing  the  gastrovascular  cavity  of 
the  Hydra,  but  with  no  genuine  mouth,  the  pores  or  so- 
called  mouths  simply  allowing  the  sea-water  laden  with 
sponge-food  to  flow  in,  inflowing  currents  being  formed  by 
the  ciliary  action  of  the  digestive  cells,  and  the  excurrent 
orifice  permitting  its  exit. 

In  the  other  sponges  such  as  are  figured  in  this  chapter, 
the  structure  is  a  little  more  complicated  than  in  the 
Ascetta.  There  is  no  general  body-cavity,  with  a  contin- 
uous lining  of  epithelial  cells,  but  the  entire  sponge- mass  is 
permeated  by  large  canals  ending  in  oscula,  and  there  are 
innumerable  pores  (so-called  mouths)  leading  by  branching 
canals  to  little  pockets  or  cavities,  which  are  lined  with  the 
flagellate,  collared  cells  developed  specially  from  the  inner 
cell-layer  (endoderm)  ;  so  that  the  animal  is  myriad-stom- 
ached, so  to  speak.  Moreover,  the  middle  layer  of  cells  is  in 
many  sponges  greatly -thickened,  and  nearly  the  whole 
mass,  as  seen  in  the  common  sponge,  consists  of  spicules  or 
horny  fibres,  and  protoplasm,  through  which  the  excurrent 
and  incurrent  channels  meander.  Thread  cells  or  lasso- 
cells  like  those  hereafter  to  be  described  in  Hydra  have 
been  detected  in  the  sponge  named  Reniera. 

Let  us  now  follow  out  the  life-history  of  a  sponge.  The 
sponges  are  further  distinguished  from  the  Protozoa  in  pro- 
ducing eggs  and  spermatic  particles,  the  eggs  being  fertilized 
before  leaving  the  sponge.  The  egg  after  fertilization  di- 
vides in  two,  four,  eight,  sixteen,  and  more  spheres,  attain- 
ing the  mulberry  or  morula  *  state  (Fig.  29).  The  result  is 

*  The  terms  marult  and  gastrulti  are  used  in  this  book  simply  for 


44 


ZOOLOGY. 


the  formation  of  a  two  and  afterward  three-layered  sac,  cor- 
responding to  the  gastrula  of  the  higher  animals.  In  this 
state  (Fig.  30)  the  germ  breaks  out  of  the  parent  sponge  into 
the  sea.  Fig.  31  represents  the  development  of  the  common 
little  calcareous  sporge  (Sycon  ciliatum),  found  between 
tide-marks.  A  indicates  the  morula  with  the  segmentation  - 

cavity  (c),  which  afterward 
disappears  as  at  B.  The 
gastrula  is  represented  at 
(7,  and  consists  of  ciliat- 
ed and  non-ciliated  large 
round  cells  ;  the  first  series 

Fig.  ^.-Segmentation  of  egg  of  sponge    forming  a  Sort  of  arch,  With 
(Halisarca).—  After  Carter.  -.     n  •  -JJT 

a    hollow  in    the  middle, 

around  which  a  large  number  of  very  fine  brown  pigment 
corpuscles  are  collected.  The  next  change  of  importance  is 
the  disappearance  of  the  cavity,  the  upper  or  ciliated  half 
of  the  body  being  much  reduced  in  size.  Then  the  large 
round  cells  of  the  hinder  part  are  united  into  a  compact 
mass,  leaving  only  a  single  row.  The  ciliated  cells  are 
gradually  withdrawn  into  the 
body-cavity.  Fig.  31,  />,  shows 
this  process  going  on.  At  this 
period  also  the  larva  becomes  ses- 
sile, and  now  begins  the  formation 
of  the  sponge-spicules,  which  de- 
velop from  the  non-ciliated  round 
cells.  Metschnikoff  calls  atten- 
tion to  the  fact  that  at  this  early 
stage  the  Sycon  passes  through  a 
phase  which  is  persistent  in  the  Pig.  3o._Ga8trulaof  aeponge(^. 

genUS  SlJCySSCt.      The  layer  Of  cil-  candra  raphanus).— After  Schulze. 

iated  cells  are  gradually  withdrawn  into  the  body-cavity, 
until  a  small  opening  is  left  surrounded  with  a  circle  of 
cilia.  These  cilia  finally  disappear,  a  few  more  spicules 
grow  out,  and  meanwhile  the  opening  disappears.  In  the 
next  stage  (represented  at  D}  a  considerable  body-cavity  ap- 

convenience  to  avoid  circumlocution.  It  may  be  that  these  conditions 
will  l)e  found  to  be  essentially  modified  in  different  groups  of  animals, 


DEVELOPMENT  OF  SPONGES. 


45 


pears  which  may  be  seen  through  the  body- walls.  At  this 
time  the  germ  consists  of  two  layers,  the  inner  layer  of  cili- 
ated cells  (endoderm)  forming  a  closed  sac,  enveloped  in  the 
spiculiferous  layer.  Such  are  the  observations  of  Metschni- 
koff  on  the  development  of  Sycon.  According  to  the  ob- 
servations of  Barrois,  the  larva  or  gastrula  fixes  itself  by  what 
are  destined  to  be  the  ectodermal  cells,  and  which  are  the 
round  non-ciliafced  cells  forming  the  posterior  end  (Fig.  31, 
C)  of  the  free-swimming  gastrula.  About  this  time  the 
mesoderm  separates  from  the  endoderm,  either  before  or 
just  after  the  gastrula  becomes  stationary,  according  to  the 
group  to  which  it  belongs. 

When  the  young  sponge  becomes  stationary  it  does  not 
differ  from  the  gastrula,  except  that  it  becomes  more  or  less 


Fig.  31.— Development  of  a  sponge  (Sycon  ciliatum).—  After  Metschuikoff . 

irregular  in  form.  Then  appear  the  food  or  digestive  cavi- 
ties in  the  endoderm,  in  Sycandra  becoming  radiating  tubes 
lined  with  ciliated,  collared,  monad-like  cells  ;  or  in  Leucon 
and  Hcdichondria,  and  their  allies,  forming  scattered  pock- 
ets, called  ' '  ampullaceous  sacs. "  Inmost  sponges  (except 
some  calcareous  species)  there  is  no  general  body-cavity  in 
the  gastrula,  nor  in  the  young  after  the  larva  becomes  sta- 
tionary, according  to  Barrois.  After  the  formation  of  the 
ampullaceous  sacs  the  pores  open  through  the  mesoderm 
and  connect  the  sacs  and  ciliated  channels,  as  the  case  may 


46  ZOOLOGY. 

be,  with  the  outer  world.  These  pores  may  open  and  then 
be  permanently  closed,  new  ones  opening  elsewhere.  The 
osculum  bursts  open  by  the  accumulation  of  water  between 
the  two  layers  in  the  same  manner  as  the  pores.  Finally, 
in  certain  sponges  the  horny  fibres  grow  out  from  the  outer 
cell-layer  and  extend  inward,  surrounding  the  spicules,  the 
latter  developing  from  the  middle  cell-layer. 

It  appears,  also,  that  all  sponge  embryos  form  a  two  and 
afterward  three-layered  sac  (gastrula),  in  which  in  the  sim- 
plest sponges  there  is  a  primitive  body-cavity  and  a  prim- 
itive mouth,  while  in  the  higher  calcareous  sponges  and  in 
the  silicious  forms  the  body  -  cavity  is  only  temporarily 
open,  being  afterward  filled  up  by  the  interior  ciliated 
cells,  and  thus  forming  a  compact  mass. 

In  the  sponges,  also,  the  larva  or  free-swimming  young 
is  a  three-layered  sac,  which  is  either  hollow  or,  more  com- 
monly, solid,  and  may  attach  itself  at  the  end  of  its  free- 
swimming  life  by  one  end  to  some  fixed  object.  The  body- 
cavity  may  persist  in  the  simpler  forms  through  life,  though 
in  most  sponges  there  is  no  genuine  digestive  cavity,  but  a 
large  series  of  minute  digestive  sacs  communicating  by  canals 
with  the  large  ones  leading  to  the  oscula.  The  more  or  less 
regular  spherical  form  of  the  young  of  most  sponges  becomes 
lost  as  they  grow  ;  they  become  irregular  in  form,  encrust- 
ing rocks,  and  their  development  retrogrades  rather  than 
advances. 

In  the  fresh-water  Spongilla  there  is  a  special  provision  for 
the  maintenance  of  the  species.  In  autumn  are  formed  the 
so-called  "  seed,"  being  capsules  in  which  are  enclosed  eggs 
which  in  the  spring  develop  young  sponges.  This  cyst  or 
capsule  may  be  compared  to  the  buds  or  winter  eggs  of  the 
Polyzoa  or  of  the  water-flea  (Daphnia). 

From  the  members  of  the  next  branch,  the  sponges  differ 
in  the  great  irregularity  of  their  form,  the  lack  of  a  definite 
digestive  cavity  and  of  tentacles. 

Order  1.  Calcispongice. — The  sponges  may  conveniently 
be  divided  into  two  orders.  Those  belonging  to  the  first 
secrete  spicules  of  lime,  and  there  are  no  digestive  or  ampul- 
laceous  sacs,  but  the  minute  canals  are  lined  with  ciliated  cells. 


SPONGES.  47 

The  calcareous  sponges  are  few  in  number  and  are  repre- 
sented by  a  delicate  little  white  sponge  called  Sycon  cilia- 
turn  Johnston,  very  common  on  sea-weeds  between  tide- 
marks. 

Order  2.  Carneospongice. — In  this  group  the  spicules 
may  either  be  fibrous  and  horny  or  silicions.  The  middle 


Pig.  32.—Axinella  polypoides.  Fig.  W.—ffyalonema  boreale, 

natural  size.— After  Loven. 

cell-layer  is  very  thick,  the  endoderm  being  restricted  to  the 
numerous  digestive  cavities  or  so-called  ampullaceous  sacs. 

The  fresh-water  sponge  (Spongilld)  occurs  everywhere 
on  submerged  sticks  and  stones  in  running  or  nearly  stag- 
nant water,  usually  branching.  With  the  exception  of 
Spongilla  and  another  form,  Siphydora  echinoides  Clark, 
which  grows  as  large  as  one's  fist  in  northern  ponds  and 
streams,  all  sponges  are  marine.  One  of  the  commonest 


48 


ZOOLOGY. 


sponges  north  of  New  York  is  CJialinula  oculata  (Bower- 
bank),  which  grows  in  long  slender  branches  on  the  piles  of 
wharves  and  bridges.  Allied  to  it  is  Axinella  (Fig.  32,  A. 
polypoides). 

Allied  to  Tethea,  which  is  sessile,  is  a  deep-sea  form  grow- 
ing on  a  long  stalk,  i.e.,  Stylocordyla  boreale  (Fig.  33).  At 
the  depth  of  100  fathoms  in  the  Gulf  of  Maine  occurs  a 


Fig.  M~PheroMma  Anna,  half  natural  size,  with  stellate  and  anchor-like  Bpicules 
uch  enlarged.—  After  Leidy. 


similar  species  (&  longissimum  Sars).  Fig.  34  represents 
a  fine  silicious  sponge  (Pheronema  Anna  Leidy)  from  the 
West  Indies.  The-  most  beautiful  of  all  silicious  sponges  is 
the  Venus'  flower-basket  (Euplectellum  aspergillum),  which 
lives  anchored  in  the  mud  at  the  depth  of  about  10  fathoms, 
near  the  Philippine  Islands. 


COMMERCIAL  SPONGES.  49 

The  Cliona  bores  into  shells,  causing  them  to  disinte- 
grate. For  example,  Cliona  sulphured,  of  Verrill  has  been 
found  by  him  boring  into  various  shells,  such  as  the  oyster, 
mussel,  and  scallop  ;  it  also  spreads  out  on  all  sides,  envelop- 
ing and  dissolving  the  entire  shell.  It  has  even  been  found 
to  penetrate  one  or  two  inches  into  hard  statuary  marble. 

Of  the  marketable  sponges  there  are  six  species,  with  nu- 
merous varieties.  They  are  available  for  our  use  from  being 
simply  fibrous,  having  no  silicious  spicules.  The  Mediter- 
ranean sponges  are  the  best,  being  the  softest;  those  of  the 
Red  Sea  are  next  in  quality,  while  our  West  Indian  species 
are  coarser  and  less  durable.  Our  glove-sponge  (Spongia 
tubulifera  Duch.  and  Mich.)  corresponds  to  Spongia  Adriat- 
ica  Schmidt,  which  is  the  Turkey  cup-sponge  and  Levant 
toilet  sponge  of  the  Mediterranean.  Spongia  gossypina 
Duch.  and  Mich,  the  wool  sponge  of  Florida  and  the  Baha- 
mas, corresponds  to  S.  equina  Schmidt,  the  horse  or  bath 
sponge  of  the  Mediterranean. 


BRANCH  II.— PORIFERA. 

The  sponges  are  many-celled  animals,  with  three  cell-layers,  without  a 
true  digestive  cavity,  supported  usually  by  calcareous  or  silicious  spicules, 
the  body-mass  permeated  by  ciliated  passages,  01*  containing  minute  cham~ 
bers  lined  by  ciliated,  collared,  monad-like  cells.  No  true  mouth-opening, 
but  usually  an  irregular  system  of  inhalent  pores  opening  into  the  cell-lined 
chambers  or  passages  through  which  the  food  is  introduced  in  currents  of 
sea-water,  tlie  waste  particles  passing  out  of  the  body  by  a  single,  but  more 
usually,  many  cloacal  openings  (oscula).  Sponges  are  hermaphroditic,  mul- 
tiplying by  fertilized  eggs,  the  germ  passing  through  a  morula  and  a  gastrula 
stage.  (The  characters  of  the  Class  the  same  as  those  of  the  Branch.) 

Order  1.  Calcispongia.  Animal  supported  by  a  framework  of  calcare- 
ous spicules,  disposed  in  lines  or  columns  at  right  angles  to 
the  walls  ;  with  cell-lined  radiating  canals.  (Sycon.) 

Order  2.  Carneospongi®.  Mesoderm  exceedingly  thick  ;  the  ciliated 
cells  restricted  to  cell -lined  chambers.  Either  no  solid 
framework,  as  in  Halisarca,  or  usually  a  well-developed 
fibrous  or  silicious  framework.  (Spongilla,  Spongia,  Hya- 
lonema,  Euplectella.) 


50  ZOOLOGY. 

VIEW  OP  THE  CLASSIFICATION  OF  THE  PORIFEBA. 

CarneospongicB. 
(SpongiaJ 

CaldspongiCB. 
(Sycon.) 


POKIFERA. 

Laboratory  Work.— Sponges  are  difficult  to  preserve  alive  in  aquaria 
for  study.  Fine  microscopic  sections  of  the  living  sponge  may  be  made 
with  the  razor  or  the  microtome,  and  the  tissues  and  eggs  as  well  as  the 
young  be  studied,  though,  from  their  minuteness,  the  study  of  the 
young  is  very  difficult.  The  ciliated  young  of  Sycon  dliatum  may  be 
obtained  in  the  spring  and  summer  by  picking  a  portion  of  the  sponge 
to  pieces  and  tearing  out  small  fragments  with  fine  needles,  until  por- 
tions are  small  enough  to  be  examined  under  high  powers  of  the  micro- 
scope. Researches  on  the  finer  structure  and  mode  of  growth  of  the 
sponge  are  difficult,  and  require  much  skill  and  long  training  in  his- 
tological  methods.  The  gross  structure  of  sponges  may  be  studied  by 
cross  and  longitudinal  sections  made  with  a  razor  or  knife. 


CHAPTER   III. 


BRANCH    III.—  CCELENTERATA  (HYDROIDS,   JELLY 
FISHES  AND  POLYPS). 


General  Characters  of  Coelenterates.—  In  this  branch, 
which  is  represented  by  animals  like  the  Hydra  (Fig.  36)  and 
Tubular  ia  (Fig.  35),  the  body  consists 
of  three  cell-layers,  surrounding  a 
definite,  single,  digestive  cavity,  the 
mouth  of  the  cavity  being  surrounded  ct\ 
by  a  circle  of  tentacles,  which  are  hol- 
low and  connect  directly  with  the 
stomach.  The  latter,  however,  is  only 
partly  differentiated  or  set  apart  from 
the  body,  hence  the  name  C&Unterata 
(Greek,  HozAo?,  hidden,  and  s'vrepov, 
digestive  tract).  From  the  stomach 
often  radiate  water-  vascular  canals,  no 
blood-system  yet  appearing  thus  far  in 
the  animal  kingdom,  the  products  of 
digestion  reaching  the  tissues  from 
the  smaller  branches  of  the  primary 
water-vascular  canals.  The  nervous 
system  is  either  absent,  or  in  different 
grades  of  development,  from  the  iso- 
lated nervo-muscular  cells  of  Hydra 
and  the  scattered  nerve-cells  of  an 
Actinia,  to  the  continuous  ganglion- 
ated  nervous  ring  of  the  minute  From  Tenneys  zoology. 
jelly-fish  such  as  Sarsia.  These  animals  display  a  striking 
amount  of  radial  symmetry,  the  organs  and  body  being  dis- 
posed in  a  radiate  manner  around  a  central  vertical  axis,  in 


M  ZOOLOGY. 

part  formed  by  the  digestive  tract.  The  Coelenterata  pre- 
sent striking  examples  of  self-division,  gemmation,  and 
alternate  generations,  and  very  great  extremes  in  degree  of 
complexity  of  structure. 

The  different  groups  have  a  high  geological  antiquity; 
the  species  of  Hydroid  and  coral-polyps  serving  as  time- 
marks  to  measure  off  geological  periods. 


CLASS  I. — HYDROZOA  (Hydroids  and  Acalephs.) 

General  Characters  of  Hydrozoa.— An  excellent  idea  of 
the  general  structure  of  the  Hydrozoa  may  be  obtained  from 
a  study  of  Hydra,  the  type  or  example  of  the  whole  class,  all 
the  other  forms  being  but  a  modification  and  elaboration  of 
this  simple  type.  The  characters  of  the  class  as  a  whole  are 
based  on  what  is  found  to  constitute  the  structure  of 
Hydra. 

Order  1.  Hydroidea. — The  animal  next  higher  in  struc- 
ture than  the  sponge  is  the  curious  Protohydra  discovered 
by  Greef  among  diatoms  and  sea-weeds  at  Ostend.  It  is  re- 
garded by  Greef  as  the  marine  ancestral  form  of  the  Coelen- 
terates.  It  is  the  simplest  Coalenterate  yet  discovered.  As 
the  form  of  the  fresh-water  Hydra  is  familiar,  Protohydra 
may  be  best  described  as  being  similar  to  that,  except  that 
it  is  entirely  wanting  in  tentacles.  It  is  made  up  of  two 
layers  (an  ectoderm  and  endoderm,  no  mesoderm  having  yet 
been  discovered),  with  a  mouth  and  stomach  (gastro-vascular 
cavity). 

A  more  complicated  form  is  the  fresh-water  Hydra,  which 
is  commonly  found  on  the  under  side  of  the  leaves  of  aquatic 
plants.  There  are  two  varieties  of  Hydra  vulgaris  appar- 
ently common  to  the  fresh  waters  of  the  old  and  new  world  ; 
they  are  Hydra  viridis  and  fusca.  The  somewhat  club- 
shaped  body  consists  of  two  layers,  the  inner  (endoderm) 
lining  the  general  cavity  of  the  body,  which  serves  both  as 
mouth  and  stomach,  as  well  as  for  the  circulation  of  the 
nutritive  fluid,  and  is  called  the  gastro-vascular  cavity. 
The  mouth  is  surrounded  with  from  five  to  eight  tentacles, 


STRUCTURE  OF  IIYDRA.  53 

which  are  prolongations  of  the  body-wall,  and  are  hollow, 
communicating  with  the  body-cavity. 

Such  is  the  general  structure  of  the  Hydra.  In  the 
ectoderm  are  situated  the  lasso-cells  or  nettling  organs,  be- 
ing minute  barbed  filaments  coiled  up  in  a  cell-wall,  which 
may  be  thrown  out  so  as  to  paralyze  the  animals  serving  as 
food.  While  the  endoderm  forms  a  simple  cell-layer,  the 
outer  layer  (ectoderm)  is  more  complex,  as  just  within  an 
external  simple  layer  of  large  cells  is  a  multitude  of  smaller 
cells,  some  of  them  being  thread  or  lasso-cells,  while  still 
within  are  fine  muscular  fibrillae  which  form  a  continuous 
layer.  The  large  cells  first  named  end  in  fibre-like  pro- 
cesses, which  alone  possess  contractility,  and  are  thought  by 
Kleinenberg  to  be  motor-nerve  endings.  These  large  cells, 
from  combining  the  functions  of  muscle  and  nerve,  are 
termed  "  nervo-muscle  cells."  The  little  cavities  between 
the  large  endodermal  cells  and  the  muscular  layer  (meso- 
derm?)  which  lies  next  to  the  endoderm  are  filled  with 
small  cells  and  lasso-cells,  forming  what  Kleinenberg  calls 
the  interstitial  tissue.  From  this  tissue  are  developed  the 
eggs  and  sperm-cells. 

The  body  being  but  slightly  differentiated  or  set  apart 
into  special  organs,  the  Hydra,  like  other  low  creatures,  is 
capable  to  a  wonderful  degree  of  reproducing  itself  when 
artificially  dissected.  Trembley,  in  1744,  described  in  his 
famous  work  how  he  not  only  cut  Hydras  in  two,  but  on 
slicing  them  across  into  thin  rings,  found  that  from  each 
ring  grew  out  a  crown  of  tentacles;  he  split  them  into  lon- 
gitudinal strips,  each  portion  becoming  eventually  a  well- 
shaped  Hydra,  and  finally  he  turned  them  inside  out,  and 
in  a  few  days  the  evaginated  Hydra  swallowed  pieces  of 
meat,  though  its  old  stomach-lining  had  now  become  its 
skin.  We  shall  see  that  not  only  many  Hydroids,  Aca- 
lephs,  some  Echinoderms,  and  many  worms,  may  reproduce 
lost  parts  and  suffer  artificial  dissection,  but  that  self- 
division  is  a  normal  though  unusual  mode  of  reproduction 
among  these  animals,  as  well  as  in  the  Protozoa,  which 
may  also  be  made  to  reproduce  by  artificial  division,  as 
Ehrenberg  cut  an  inf usorian  into  several  pieces,  each  frag- 
ment becoming  a  perfect  individual. 


ZOOLOGY. 


The  process  of  budding  is  but  a  modification  of  that  in- 
volved in  natural  self -division,  and  it  is  carried  on  to  a  great 
extent  in  Hydra,  a  much  larger  number  of  individuals  being 
produced  in  this  way  than  from  eggs.  Our  figure  (36) 
shows  two  individuals  budding  out  from  the  parent  Hydra ; 

the  smaller  bud  (a)  is 
a  simple  bulging  out 
of  the  body-walls,  the 
bud  enveloping  a  por- 
tion of  the  stomach, 
until  it  becomes  con- 
stricted and  drops  off, 
the  tentacles  mean- 
while budding  out 
from  the  distal  end, 
and  a  mouth-opening 
arising  between  them, 
as  at  c.  Budding  in 
the  Hydra,  the  Acti- 
nia, and,  in  fact,  all 
the  lower  animals,  is 
simply  due  to  an  in- 
crease in  the  growth 
and  multiplication  of 
cells  at  a  special  point 
on  the  outside  of  the 
body,  while  the  asex- 
ual mode  of  reproduc- 
tion in  the  Aphis  and 
a  few  other  insects 
results  from  the  inul- 

Of 


ovary)  in  the  inside  of 
the  body.  Thus  Parthenogenesis  or  Agamogenesis  is  analo- 
gous to  the  ordinary  mode  of  budding.  Ehrenberg  first  showed 
that  the  Hydra  reproduces  by  fertilized  eggs.  Kleinenberg 
describes  the  testis,  which  is  lodged  in  the  ectoderm,  and 
which  develops  tailed  spermatozoa  like  those  of  the  higher 


DEVELOPMENT  OF  HYDRA.  55 

animals.  They  arise,  as  in  other  higher  animals,  from  a 
self-division  of  the  nuclei  of  the  testis-cells.  There  is  a  true 
ovary  formed  in  the  same  interstitial  tissue  of  the  ectoderm, 
consisting  of  a  group  of  cells,  which,  Kleinenberg  states, 
differ  entirely  in  their  mode  of  formation  from  the  ovaries 
(gonopliores)  of  the  marine  hydroids^  which  are  genuine 
buds. 

It  thus  seems  that  Hydra  is  monoecious  or  hermaphro- 
dite— i.e.,  the  sexes  are  not  distinct.  The  egg  of  Hydra 
originates  from  the  central  cell  of  the  ovary. 

There  is  a  true  segmentation  of  the  egg.  The  young 
Hydra  thus  passes  through  a  true  morula  stage:  There 
is  tin  outer  layer  of  prismatic  cells,  forming  the  surface  of 
the  germ,  and  surrounding  the  inner  mass  of  polygonal 
cells.  At  first  none  of  these  cells  are  nucleated,  but  after- 
ward nuclei  appear,  and  it  is  an  important  fact  that  these 
nuclei  do  not  arise  from  any  pre-existent  egg-nucleus. 

The  next  step  is  the  formation  of  a  true  chitinous  shell,' 
enveloping  the  germ  or  embryo.  After  this,  Kleinenberg 
asserts  that  the  cells  of  the  germ  become  fused  together, 
and  that  the  germ  is  like  an  unsegmented  egg,  being  a 
single  continuous  mass  of  protoplasm. 

The  remaining  history  of  Hydra  is  soon  told.  In  this 
protoplasmic  germ -mass  there  is  formed  a  small  excentric 
cavity  ;  this  is  the  beginning  of  the  body-cavity,  which 
finally  forms  a  closed  sac.  After  several  weeks  the  germ 
bursts  the  hard  shell  and  escapes  into  the  surrounding  wa- 
ter, but  is  still  surrounded  by  a  thin  inner  shell.  After  this 
a  clear  superficial  zone  appears,  and  a  darker  one  beneath, 
which  is  the  first  indication  of  the  splitting  of  the  germ  into 
the  two,  afterward  three,  definitive  germ-lamellse,  common 
to  all  animals  except  the  one-celled  Protozoa. 

The  embryo  soon  stretches  itself  out,  a  star-shaped  cleft 
appearing,  which  forms  the  mouth.  The  tentacles  next  ap- 
pear. The  animal  now  bursts  open  the  thin  inner  shell, 
and  the  young  Hydra  appears  much  like  its  parent  form. 

There  is,  then,  no  metamorphosis  in  the  Hydra  ;  no  cili- 
ated planula,  as  in  many  other  Hydroids.  The  adult  form 
is  thus  reached  by  continuous  growth. 


56  ZOOLOGY. 

It  will  be  seen,  to  anticipate  somewhat,  that  the  Hydra, 
exactly  as  in  the  vertebrates,  including  man,  arises  from  an 
egg  developed  from  a  true  ovary,  which,  after  fertilization, 
passes  through  a  morula  stage  ;  that  the  germ  consists  at 
first  of  two  germinal  layers,  while  from  the  outer  layer,  as 
probably  in  the  vertebrates,  an  intermediate  or  nervo-mus- 
cular  layer  is  formed,  which  Allman  thinks  is  thehomologue 
of  the  middle  germ-lamella  of  the  vertebrates  (mesoderm) 
supposed  to  have  originally  split  off  from  the  ectoderm. 

In  all  the  other  Hydroids  the  sexes  are  separate,  and  we 
for  the  first  time  in  the  animal  kingdom  meet  with  two 
sorts  of  individuals — i.e.,  males  and  females. 


^acW"*a  echinat<*  °n  a  shell  tenanted  by  a  hermit  crab, 
m's  Thierleben. 


The  simplest  form  next  to  Hydra  is  Hydractinia,  in 
which  the  individual  is  differentiated  into  three  sets  of 
zooids— i.e.,  a,  hydra-like,  sterile  or  nutritive  zooids  ;  I  and 
c,  the  reproductive  zooids,  one  male  and  the  other  female, 
both  being  much  alike  externally,  having  below  the  short 
rudimentary  tentacles  several  spherical  sacs,  which  pro- 
duce either  male  or  female  medusa?.  These  medusa-buds 
(gonophores)  are  in  structure  like  the  free  medusae  of  Co- 
ryne.  The  marine  Hydroids,  then,  are  usually  sexually  dis- 
tinct, growing  by  colonies,  which  are  either  male  or  female. 


HYDROID   CORALS. 


57 


Hydr actinia  ecJiinata  (Fig.  37)  forms  masses  (each  called  a 
hydrophyton)  encrusting  shells. 

In  Clava  the  reproductive  buds  remain  permanently  at- 
tached. It  grows  in  pink  masses  on  Fucoids,  about  half  an 
inch  high,  and  is  very  common  on  our  shores.  It  is  repre- 
sented in  fresh  water  by  Cordylophora  lacustris  Allman, 
which  lives  attached  to  rocks  and  plants  in  Europe  and  this 
country. 

Here  comes  in  the  group  of  Hydroids  represented  by 
Millepora  and  Stylaster,  which  were  formerly  considered  to 
be  Anthozoan  corals.  By  the  researches  of  L.  Agassiz  in 
1859,  and  H.  M.  Moseley 
in  1876,  Millepora,  which 
had  been  confounded 
with  the  coral  polyps, 
has  been  proved  to  be  a 
Hydroid  allied,  as  Agas- 
siz stated,  to  Hydr  acti- 
nia. Like  that  Hydroid, 
it  forms  a  calcareous 
encrusting  mass,  but  of 
much  greater  extent,  a 
considerable  proportion 
of  the  coral  in  the  Flori- 
da reefs  being  formed 
by  the  Millepora.  Our 
American  species  is  Mil- 
lepora alcicornis  Linn., 
while  our  description  is  taken  from  Moseley's  account  of 
Millepora  nodosa  Esper.  (Fig.  38).  Its  generic  name  is  de- 
rived from  the  numerous  pores  or  calicles  dotting  its  surface 
and  arranged  in  irregular  circular  groups,  consisting  of  a 
central  calicle,  or  cup-like  hollow,  with  from  five  to  eight 
smaller  calicles  arranged  around  it.  The  mass  of  the  coral, 
or  hydrophyton,  consists  of  fibres  (or  trabeculae)  of  lime, 
forming  a  spongy  mass,  traversed  in  all  directions  by  tor- 
tuous canals  which  "  form  regular  branching  systems  with 
main  trunks,  giving  off  numerous  branches,  from  which 
arise  secondary  branches,  and  from  these  again  smaller 


38.— Millepora   nodosa.      a,   nutritive 
6,  reproductive  zooid  ;  c,  lasso-cell ;  d, 
the  same  coflcd  up  in  its  cell ;  e,  a  third  form. 


58  ZOOLOGY. 

ramifications.  The  whole  canal  system  is  connected  to- 
gether by  a  freely  anastomosing  mesh-work  of  smaller  ves- 
sels, and  communicates  freely  by  numerous  offsets  with  the 
cavities  of  the  calicles."  As  the  animals  increase  in  num- 
bers and  die,  the  coral  stock  increases  in  size,  the  layer  con- 
taining the  living  animals  forming  a  thin  film  only,  the 
bottom  of  the  little  cups  or  pores  forming  a  table  or  plat- 
form, whence  the  term  Tdbulata,  originally  applied  to  this 
group,  the  old  calicles  being  divided  by  a  series  of  trans- 
verse plates  or  laminae,  separating  them  into  series  of  cham- 
bers. Moseley  shows  that  the  corallum  of  Millepora  is  dis- 
tinguished from  all  other  coralla  by  its  systems  of  canals 
branching  in  an  arborescent  manner,  while  the  tabulate 
structure  occurs  in  certain  Alcyonaria,  Zoantharia,  and  in 
other  Hydroida ;  hence  the  group  Tabulata,  as  previously 
stated  by  Verrill,  is  an  artificial  one. 

The  animals  of  the  Millepora  are  of  two  kinds  ;  those  in- 
habiting the  central  cup  or  pore  are  short,  thick  zooids, 
with  a  mouth  and  four  tentacles,  and  only  half  a  milli- 
metre in  height ;  those  in  the  smaller  pores  are  longer  and 
slenderer,  about  one  and  a  half  millimetres  in  height,  with 
from  usually  five  to  twenty  tentacles,  situated  at  irregular  in- 
tervals from  the  base  to  the  summit  of  the  body.  The  body 
cavities  of  the  zooids  end  in  blind  sacs  at  the  uv/otom  of  the 
cup,  but  are  continuous  beyond  with  the  canals  of  the  hy- 
drophyton,  the  latter  being  defined  by  Allman  as  forming 
in  the  Hydroids  "  the  common  basis  by  which  the  several 
zooids  of  the  colony  are  kept  in  union  with  one  another/' 
As  we  know  nothing  of  the  mode  of  reproduction  of  Mille- 
pora, we  must  leave  it  for  the  present  near  Hydractinia,  to 
which  the  adult  animals  are  nearest  related.  Moseley  also 
discovered  that  Sty laster,  a  beautiful  pink  coral  which  grows 
at  Tahiti,  with  the  Millepora,  is  in  reality  a  Hydroid,  and 
not  a  true  coral  polyp,  as  has  always  been  supposed.  That, 
finally,  Millepora  is  a  true  Hydroid  is  proved,  Moseley  thinks, 
by  the  peculiar  structure  of  the  hydrophyton,  the  forms  of 
the  zooids,  the  absence  of  all  trace  of  mesenteries,  the  ap- 
parent septa  present  in  the  tentacles,  and  by  the  presence 
of  thread-cells  of  the  form  peculiar  to  "the  Hydrozoa.  The 


DEVELOPMENT  OF  HYDEOIDS. 


59 


Fig.  39.  —  Polypite  of 
Coryne  mira bills,  with  a  bud 
below  a,  and  medusa-bud 
(gouophore)  at  a.  Much  en- 
larged.—After  Agassiz. 


living  Millepora,  unless  handled  with  great  care,  severely 
stings  the  hand  of  the  collector. 

We  now  come  to  Hydroids  which  throw  off  a  free  naked- 
eyed  medusa  from  the  hydrarium  (Fig. 
39).  From  the  centre  of  these  free 
bell-shaped,  minute  jelly-fishes  depends 
a  hollow,  open  sac  called  the  manu- 
brium,  the  cavity  of  which  (stomach) 
opens  into  usually  four  canals,  which 
radiate  from  the  hollow  or  stomach  in 
the  centre  of  the  disk  and  communi- 
cate with  a  canal  following  the  margin 
of  the  disk.  This  is 
the  water- vascular  sys- 
tem, communicating 
directly  with  the  gas- 
tro-vascular  cavity,  or 
stomach.  Four  tenta- 
cles hang  from  the 
disk,  and  simple  eye- 
spots  and  otolithic  sacs  (simple  ears)  are  usu- 
ally present  and  situated  at  regular  inter- 
vals around  the  edge  of  the  disk.  Such  is 
the  typic?^  form  of  all  the  free-swimming 
Hydroids.  They  are  said,  in  a  few  cases, 
to  possess  a  well-developed  continuous  ner- 
vous system,  consisting  of  a  nervous  ring 
around  the  disk  (Romanes).  They  are  bi- 
sexual, the  ovaries  or  spermaries  being  de- 
veloped on  the  radiating  canals,  the  embryo 
escaping  into  the  surrounding  water  by  rup- 
turing the  walls  of  the  ovary. 

The  young  is  at  first  oval,  ciliated  all 
over  the  surface  of  the  body,  and  is  called  a  \  \ 

planula.     The  planula,  as  in  Melicertwn,  a  Fig.  40.— Free  Medu- 
genus  allied  to  Campanularia,  and  a  type 
of  most  marine  Hydroids,  at  first  spherical,  becomes  pear- 
shaped,  and  after  swimming  about  for  a  time  attaches  itself 
to  some  object.     It  then  elongates,  a  horny  sheath  (peri- 


60 


ZOOLOGY. 


sarc)  forms  around  it,  tentacles  arise  around  the  mouth, 
finally  the  stem  branches,  new  Hydroids  arise,  until  a  hy- 
droid  community  (consisting  of  trophosomes  and  gonosomes) 
is  formed,  and  in  the  following  spring  medusa-buds  (gono- 
phores)  arise,  which  become  free  (medusoids),  and  thus  the 
reproductive  cycle  is  completed.  The  developmental  his- 
tory of  this  Hydroid  is  a  good  example  of  what  is  called 
"  alternation  of  generations." 

Budding  occurs  in  the  medusa  of  Sarsia  prolifera,  in 
Hybocodon  prolifer  arid  Dysmorphosa  fulgurans.  Mul- 
tiplication by  fission  has  been  observed  in  the  medusa  of 
Stomobrachium  mirabile.  The  pendent  stomach  was  seen 
by  Kolliker  to  divide  in  two,  becoming  doubled,  which  act 
was  followed  by  a  vertical  division  of  the  umbrella,  separat- 
ing the  animal  into  two  independent  halves.  These  again 
subdivided,  and  Kolliker  thinks  this  process  went  on  still 
further.  Haeckel  has  found  in  cutting  off  a  portion  of  the 
edges  of  the  umbrella  of  certain  Thaumantice,  that  the  frag- 
ment in  a  few  days  became  a  complete  medusa. 
In  the  Tubularian  Hydroids  (Tubularia,  Hylocodon,  Co- 
rymorpha,  Monocaulus,  etc.,  Fig.  41), 
the  mode  of  reproduction  is  peculiar. 
From  the  medusa-buds  (sporosac)  is  set 
free  an  embryo  (actinula),  which  swims 
about  or  creeps  on  its  tentacles,  mouth 
downward.  It  then  attaches  itself  by  a 
disk-like  expansion  of  the  posterior  end, 
which  forms  a  stem  until  the  original 
Tubularia  form  is  attained. 

A  gigantic  Monocaulus  having  sessile 
ovisacs,  measuring  seven  feet  four  inches 
in  height,  and  provided  with  a  crown  of 
tentacles  nine  inches  across  from  tip  to 
tip  of  the  expanded,  non-retractile  ten- 
tacles, was  dredged  by  the  Challenger 
Expedition  at  the  depth  of  four  miles. 
Ailman  suggests  that  such  a  deep-sea  Hydroid  could  not,  on 
account  of  the  darkness  and  pressure  of  the  water  at  such  a 
great  depth,  produce  free-swimming  medusae.  In  Tiaropsis 


41. — Monocaulus  pen- 
tlus.— After  Agassiz. 


GRAPTOLITES. 


there  is  no  trace  of  a  nervous  system  such  as  exists  in 
Sarsia,  where  nerve-fibres  extend  around  the  margin  and 
along  the  radial  tubes  (Romanes). 

In  the  groups  of  Campanularice,  represented  by  Plumu- 
laria,  Sertularia,  Zygodactyla,  Dynamena,  and  Campanu- 
laria,  the  ectoderm  is  protected  by  a  horny  or  chitinous 
sheath  (perisarc)  enveloping  the  zooids.  The  Hydroids  re- 
tract, when  disturbed,  into  small  cells  (hydrothecae),  arranged 
in  opposite  rows  on 
the  stalk  as  in  Sertu- 
laria  (Fig.  42),  or 
singly  at  the  ends  of 
the  stalks,  as  in  Cam- 
panularia,  while  the 
sheaths  (gonothecce) 
protecting  the  medu- 
sa-buds are  distin- 
guished by  their 
much  larger  size  and 
cup-shaped  form. 

The  Sertularians 
abound  on  sea-weeds, 
and  may  be  recogniz- 
ed from  their  resem- 
blance to  mosses. 
They  are  among  the 
most  common  objects 
of  the  seaside.  The 
medusse  of  these  and  Fjg  ^_Sertularia  abiftina  of  Europe  A  natural 

many  Other  HvdrOlds    size;  &  magnified,  showing  the  hydrarium,  with  the 
•  „      ,"-,,  cells.— From  Macallister. 

can  be  collected  by  a 

towing-net,  and  emptied  into  a  jar,  where  they  can  be  de- 
tected by  the  naked  eye  after  a  little  practice. 

Graptolites.— More  nearly  allied  perhaps  to  the  Sertularian 
Hydroids  than  any  other  known  animals  are  the  Graptolites 
(Fig.  43),  which  were  most  abundant  in  the  Lower  Silurian 
period,  and  lingered  as  late  as  the  Clinton  epoch  of  the  Upper 
Silurian.  In  Graptolithus  Logani  the  hydroid  colony  (hy- 
drosome)  is  a  long  narrow  blade,  with  a  row  of  cells  on  one 


62  ZOOLOGY. 

side  ;  in  G.  pristis  the  hydrosome  is  broader,  more  lanceo- 
late, and  the  sharp,  tooth-like  cells  are  arranged  on  both 
sides  of  a  median  stem.  In  Phyllograptus  typus  the  hy- 
drosome is  broad  and  oval,  leaf-like,  the  serrations  of  the 
leaf  marking  off  the  cells,  which  are  apparently  supported 
on  a  central  axis.  The  group  also  has  some  affinities  to  the 
Polyzoa,  and  is  probably  a  generalized  or  synthetic  type  of 
animals. 

Order  2.  DiscopJiora. — We  now  come  to  medusae  which 
differ  from  the  Hydromedusae  in 
developing  directly  from  eggs ; 
in  having  usually  no  velum  ;  with 
branching  gastro-vascular  canals, 
and  covered  sense-organs.  They 
intergrade,  however,  with  the 
Hydroidea  by  the  members  of  the 
group  or  sub-order  Trachymedu- 
sce,  represented  by  the  genera 
^Egineta,  Geryonia,  etc.  These 
are  small  jelly-fishes,  with  often 
a  remarkably  long  proboscis 
J  (manubriuni),  as  in  Geryonia, 
and  with  either  four  single  radi- 
ating canals,  or,  in  addition,  as 
in  Geryonia,  a  number  of  smaller 
canals  on  the  edge  of  the  disk  ; 
>  or,  as  in  a  still  more  complicated 
form,  Chary&daa,  the  radiating 

Pig.  ^.—Monograptua  priodon.     ponol,,    j,rp    TrrsmpViPrl     fhnQ    nnn 
c,  front  view.— After  Nicholson.  Drancnea,    tHUS 

necting  this  group  with  the  true 
covered-eyed  Acalephs,  such  as  Aurelia. 

0.  and  R.  Hertwig  have  fully  confirmed  Haeckers  discov- 
ery of  the  nature  of  the  nervous  system  in  the  Geryonidw. 
They  find  that  the  nervous  system  is  developed  in  the  ecto- 
derm and  consists  of  two  "ring-nerves"  around  the  edge 
of  the  disk,  formed  of  two  filaments,  one  lying  on  the  upper, 
the  other  on  the  under  side  of  the  velum,  immediately  at  its 
insertion.  From  this  double  nervous  ring  filaments  are  sent 
off  to  the  ganglia  near  the  sense-organs.  This  sort  of  a 


DEVELOPMENT  OF  JELLY-FISHES.  63 

nervous  system  is  present  in  the  ^EquoridcB  and  JEginidm, 
but  is  most  distinct  and  best  developed  in  the  Geryonidce 
(Glossocodon  and  Carmarina). 

The  Hertwigs  have  also  observed  in  these  Trachynemidae 
organs  of  taste,  consisting  of  groups  of  long  stiff  hairs  at 
the  base  of  the  tentacles.  They  have  been  observed  in 
Rhopalonema  velatum,  Aglaura  nemistoma,  and  in  Cunina, 
where  the  hairs  are  shorter. 

The  eggs,  in  developing,  after  total  segmentation  (morula 
state)  pass  into  a  ciliated  planula  state  as  in  Aurelia,  there 
being  at  first  apparently  no  primitive  gastric  cavity ;  the 
body  of  the  embryo  or  planula  remains  spherical,  as  in  Gery- 
onia,  these  being  a  slight  metamorphosis  ;  or,  as  in  Poly- 
xenia  and  ^ginopsis,  where  there  is  a  decided  metamor- 
phosis, the  spherical  ciliated  planula  greatly  lengthens  out 
on  each  side,  the  body  becoming  boomerang-shaped,  each 
end  of  the  boomerang  becoming  an  arm  or  tentacle.  Then 
it  becomes  a  gastrula,  a  central  cavity  and  mouth  appear- 
ing. At  right  angles  to  the  two  primitive  arms  bud  out 
two  others,  and  finally  others  appear  on  the  lower  edge  of 
the  umbrella,  and  after  slight  changes  the  adult  form  is  as- 
sumed. Cunina  is  at  first  spherical,  then,  a  single  arm 
developing,  it  becomes  club-shaped  ;  finally,  the  full  num- 
ber of  arms  grow  out,  and  the  mature  form  results.  It  ap- 
pears, then,  that  in  the  mode  of  development  from  eggs, 
without  passing  through  a  hydra-like  condition,  and  in  the 
structure  of  the  body,  the  Trachymedusce  connect  the  cov- 
ered-eyed medusas  with  the  naked-eyed  or  Hydroidea.  The 
American  forms  live  in  the  waters  of  the  Carolina  shores. 
Cunina  octonaria  McCrady  lives  in  Charleston  Harbor. 
Cunina  has  been  found  by  Haeckel  growing  on  the  columella 
of  Geryonia,  and  McCrady  has  found  that  our  native  Cunina 
is  parasitic  on  Turritopsis,  a  hydroid  medusa. 

The  Lucernarice,  or  Calycozoa,  which,  according  to  Clark, 
form  an  order  of  Acalephs,  are,  with  Huxley,  regarded  as 
a  suborder  of  Discopliora.  With  essentially  the  structure 
of  the  Aurelia  and  allies,  Lucernaria  differs  in  having  the 
power  of  attaching  itself  by  a  sucker  on  the  smaller  end  of 
its  body  to  sea-weeds,  but  can  detach  itself  at  will  and  swim. 


04  ZOOLOGY. 

about  like  the  Aurelia  by  alternate  contractions  and  expan- 
sions of  the  umbrella.  We  will  now  enter  into  a  more  com- 
plete account  of  this  group  based  on  Clark's  characteriza- 
tion. The  disk  is  more  or  less  octagonal  or  circular,  um- 
brella, funnel  or  urn-shaped,  the  end  opposite  the  mouth 
ending  in  a  pedicel,  by  which  it  is  attached  temporarily  to 
sea- weeds.  The  mouth  is  square,  and  between  the  ectoderm 
and  endoderm  is  a  jelly-like  layer  constituting  the  musculo- 
gelatiniform  layer  (mesoderm)  much  as  in  Aurelia.  This 
layer  extends  into  the  tentacles  and  marginal  anchors,  as 
well  as  into  the  pedicel.  The  cavity  of  the  disk  is  divided  into 
four  quadrant  chambers,  separated  by  as  many  partitions, 
which  extend  from  the  mouth  into  the  lobes  nearly  to  the 
margin  between  the  tentacles.  The  latter  are  arranged  in 
eight  groups  or  tufts  just  within  the  margin  of  the  disk,  at 
eight  points,  which  alternate  with  the  four  partitions  and 
the  four  corners  of  the  mouth.  The  tentacles  are  hollow, 
opening  into  the  radial  canals  of  the  general  cavity  of  the 
body,  and  end  in  a  globular  or  spheroidal  expansion,  serv- 
ing as  an  organ  of  touch  or  prehension.  In  some  forms,  as 
Haliclystus  auricula  Clark,  marginal  anchors  are  situated 
at  eight  points,  exactly  opposite  the  four  partitions  and  the 
four  corners  of  the  mouth  ;  they  are  originally  tentaculif orm, 
but  in  adult  life  form  organs  by  which  they  adhere  to  or 
pull  themselves  from  place  to  place.  The  sexes  are  distinct, 
the  reproductive  glands  having  the  same  position  in  each 
sex.  Nothing  is  absolutely  known  of  the  mode  of  growth 
of  these  animals,  but  development  is  supposed  to  be  direct. 
Our  common  Lucernarian  is  Haliclystus  auricula  Clark. 
Its  umbrella-shaped  disk  is  an  inch  in  diameter  ;  including 
the  tentacles,  an  inch  and  a  half  ;  the  pedicel  half  an  inch 
long.  It  ranges  from  Cape  Cod  to  Greenland  and  south- 
ward to  the  coast  of  England,  and  may  be  found  on  eel- 
grass  between  tide-marks. 

According  to  A.  Meyer,  the  end  of  the  stalk  when  cut  off 
produced  a  new  disk,  and  even  pieces  cut  off  between  them 
became  complete  Lucernaria},  evincing  the  extraordinary 
powers  of  reproduction  in  these  interesting  jelly-fish. 

Coming    now   to   the   true   Discophora,    jelly-fish,    sea- 


NERVOUS  SYSTEM  OF  JELLY-FISHES.  05 

nettles,  sun-fish  or  Acalephs,  of  which  there  are  about 
ninety  known  species  on  the  eastern  coast  of  the  United 
States,  we  may  study  as  the  type  of  the  suborder  the 
common  Aurelia  flavidula  Peron  and  Lesueur  of  our 
coast,  which  is  closely  allied  to  the  Aurelia  aurita  of  the 
European  shores.  It  grows  to  the  diameter  of  from  eight 
to  ten  inches,  becoming  fully  mature  in  August,  the  young 
appearing  late  in  April  in  Massachusetts  Bay,  being  then 
not  quite  an  inch  in  diameter.  The  mature  ones  may  be 
easily  captured  from  a  boat  or  from  wharves.  On  a  super- 
ficial examination,  as  well  as  by  cutting  the  animal  in  halves 
and  making  several  transverse  sections  with  a  knife,  the  lead- 
ing points  in  its  structure  may  be  ascertained.  Its  tough, 
jelly-like  disk  is  moderately  convex  and  evenly  curved,  while 
four  thick  oral  lobes  depend  from  between  the  four  large  geni- 
tal pouches  ;  the  oral  lobes  unite  below,  forming  a  square 
mouth-opening,  the  edge  of  which  is  minutely  fringed  to  the 
end  of  the  tentacles.  On  the  fringed  margin  are  eight  eyes, 
each  covered  by  a  lobule  and  situated  in  a  peduncle,  and 
occupying  as  many  slight  indentations,  dividing  the  disk 
into  eight  slightly  marked  lobes.  The  subdivisions  of  the 
water-vascular  canals  or  tubes  are  very  numerous  and  anas- 
tomose at  the  margin  of  the  disk,  one  of  them  being  in 
direct  communication  with  each  eye-peduncle.  When  in 
motion  the  disk  contracts  and  expands  rhythmically,  on  the 
average  twelve  or  fifteen  times  a  minute  ;  on  the  approach 
of  danger  they  sink  below  the  surface. 

While  a  distinct  nervous  system  has  not  been  discovered 
in  Aurelia,  Romanes  suggests  that  there  are  primitive  nervo- 
muscular  cells,  such  as  those  shown  by  Kleinenberg  to  exist 
in  Hydra,  and  he  concludes,  after  a  series  of  experiments 
on  Aurelia  aurita,  that  the  whole  contractile  sheet  of  the 
bell  presents  not  merely  the  protoplasmic  qualities  of  ex- 
citability and  contractility,  but  also  the  essentially  nervous 
quality  of  conducting  stimuli  to  a  distance  irrespective  of 
the  passage  of  a  contractile  wave.  The  later  researches  of 
0.  and  R.  Hertwig  show  that  the  nervous  system  of 
Acalephaa  (Acraspedota  or  covered-eyed  Medusae)  is  much 
more  primitive  than  in  the  naked-eyed  or  craspedote  forms, 


GG 


ZOOLOGY. 


such  as  the  medusae  of  the  Hydroids  and  the  Tracliy- 
nemidce.  In  the  European  Nausitlioe  albida,  and  Pelagia 
noctiluca  no  nerve-ring  is  present,  for  this  is  impossible 
owing  to  their  deeply  indented  disks.  There  are  instead  eight 


Fig.  44. — Gastrula  of  an  Aure- 
lia-like  Medusa,  a,  primitive 
month;  ft,  gastro-vascnlar  cavity; 
c,  ectoderm ;  d,  endoderm. — 
After  Metschnikoff. 


Fig.  45.— Scyphistoma  of  Aurelia 
Jlavidula,  at  different  ages;  magni- 
fied.— After  Agassiz. 


separate  nerve- tracts  which  unite  with  the  sense-organs  in  a 
special  elevation  of  the  edge  of  the  disk,  forming  so-called 
sense-bearers,  which  alternate  with  the  eight  tentacles. 
Aurelia  aurita  has  a  similar  disconnected  nerve  system.* 

Eimer  confirms  these  discoveries,  and  states  that  the  ner- 
vous system  in  these  Hydrozoa  arises  from  the  ectoderm. 


Fig.  46.— Strobila  of  Au- 
relia, flavidula.  —  After 
Agassiz. 


Fig.  47.  —  Ephyra  or 
earliest  free  condition  of 
Aurelia.—-  After  Agas- 
siz. 


The  Aurelia  flavidula  spawns  in  late  summer,  the  females 
being  distinguishable  by  their  yellowish  ovaries,  the  male 
glands  being  roseate,  while  the  tentacles  of  the  females  are 

*  Jenaische  Zeitschrift,  1877,  p.  355. 


DEVELOPMENT  OF  JELLY-FISHES.  67 

shorter  and  thicker  than  in  the  males.  The  eggs  pass  out 
of  the  mouth  into  the  water  along  the  channeled  arms,  and 
in  October  the  ciliated  gastrula  becomes  pear-shaped  and 
attaches  itself  to  rocks,  dead  shells,  or  sea- weeds,  and  then 
assumes  a  Hydra  form  with  often  twenty- four  very  long 
tentacles.  This  stage  was  originally  described  as  a  distinct 
animal  under  the  name  of  Scyphistoma.  In  this  Scyphis- 
toma  stage  (Fig.  45)  it  remains  about  eighteen  months. 
Toward  the  end  of  this  period  the  body  increases  in  size 
and  divides  into  a  series  of  cup-shaped  disks.  These  saucer- 
like  disks  are  scalloped  on  the  upturned  edge,  tentacles  bud 


Fig.  48.— Aurelia  flavidula.—Mter  Agassis. 

out,  and  the  animal  assumes  the  Strobila  stage  (Fig.  46). 
Finally,  the  disks  separate,  the  upper  one  becomes  detached 
and  with  the  other  disks  swims  away  in  the  Ephyra  form 
(Fig.  47),  when  about  a  fifth  of  an  inch  in  diameter,  and 
toward  the  middle  or  end  of  summer  becomes  an  adult 
Aurelia  (Fig.  48). 

Though  the  Aurelia  has  lasso-cells  it  is  not  poisonous  to 
bathers.  Not  so,  however,  with  the  gigantic  Cyanea  arctica, 
whose  long  tentacles  are  poisonous  ;  fishermen  as  well  as 
bathers  being  often  annoyed  by  them.  This  giant  jelly-fish 
sometimes  attains  a  diameter  of  from  three  to  five  feet  across 


08  ZOOLOGY. 

the  disk,  though  it  is  produced  from '  a  Scyphistoma  not 
more  than  half  an  inch  in  height.  Pelagia  campanella  and 
a  few  other  forms  do  not  undergo  this  metamorphosis,  but 
grow  directly  from  the  eggs. 

Various  boarders  or  commensals — viz.,  temporary  non- 
attached  parasites — live  in  or  under  the  mouth-cavity  or  be- 
tween the  four  tentacles  of  the  larger  Acalephs.  Such  is  the 
little  Amphipod  Crustacean,  Hyperia,  which  lives  within 
the  mouth,  while  small  fishes,  such  as  the  butter-fish,  swim 
under  the  umbrella  of  the  larger  jelly-fishes,  Cyanea,  etc.,  for 
shelter  and  protection.  Besides  small  animals  of  various 
classes,  the  larger  jelly-fishes  kill  by  means  of  their  nettling 
organs  small  cuttle-fishes  and  true  fishes,  the  animals  being 
paralyzed  by  the  pricks  of  the  minute  barbed  darts. 

Order  3.  Siphonophora. — These  are  so-called  compound 
Hydro-ids,  living  in  free-swimming  colonies,  consisting  of 
polymorphic  individuals,  or,  more  properly  speaking,  zooids 
—that  is,  organs  with  a  strongly  marked  individuality,  but 
all  more  or  less  dependent  on  each  other.  A  Siphonophore, 
such  as  Physalia,  for  example,  may  be  compared  to  a  so- 
called  colony  of  Hydractinia,  in  which  there  are  nutritive 
and  reproductive  zooids  and  medusa-buds.  In  Physalia 
there  are  four  kinds  of  zooids — i.e.  (I)  locomotive,  and  (2) 
reproductive,  with  (3)  barren  medusa-buds  (in  which  the 
proboscis  is  wanting),  which,  by  their  contractions  and 
dilatations,  impel  the  free-swimming  animal  through  the 
water  ;  in  addition,  there  are  (4)  the  feeders,  a  set  of  di- 
gestive tubes  which  nourish  the  entire  colony.  There  are 
numerous  genera  and  species  (one  hundred  and  twenty  are 
known),  whose  structure  is  more  or  less  complicated  and 
difficult  to  understand  without  many  figures  and  labored 
descriptions.  We  will  select  as  a  type  of  the  order  our 
Physalia  Aretliusa  of  Tilesius,  or  Portuguese  man-of-war 
(Fig.  49),  which  is  sometimes  borne  by  the  Gulf  Stream  as 
far  north  as  Sable  Island,  Nova  Scotia.  It  is  excessively 
poisonous  to  the  touch,  and  in  gathering  specimens  on  the 
shores  of  the  Florida  reefs  we  have  unwittingly  been  stung 
by  nearly  dead,  stranded  individuals,  whose  sting  burns  like 
condensed  fire  and  leaves  a  severe  and  lasting  smart. 


PORTUG  UESE  MAN- OF-  WA B. 


69 


The  colony  or  liydrosome  of  the  Portuguese  man-of-war 
consists  of  long  locomotive  tentacles,  which,  when  the  ani- 
mal is  driven  by  its  broad  sail  or  float  before  the  wind, 
stretch  out  in  large  individuals  from  thirty  to  fifty  feet. 
These  large  Hydra-like  zooids  are  arranged  in  small  groups, 
arising  from  a  hollow  stem  com- 
municating with  the  chymiferous 
cavity  extending  between  the  in- 
ner and  outer  wall  of  the  float. 
The  "  feeders  "  are  of  two  kinds, 
large  and  small,  and  are  clustered 
in  branches  growing  from  a  com- 
mon hollow  stem,  also  communi- 
cating with  the  chymiferous  or 
body-cavity.  L.  Agassiz,  whose 
description  of  this  animal  we  are 
condensing,  states  that  he  has 
seen  these  feeders  "gorged  with 
food  almost  to  bursting,"  but  has 
never  seen  undigested  food  in 
any  of  the  other  organs.  The 
medusa-buds  (gonophores)  arise 
from  a  third  set  of  very  small 
Hydras,  but  form  very  large  clus- 
ters suspended  between  the  clus- 
ters of  feeders.  These  reproduc- 
tive zooids  resemble  the  locomo- 
tive zooids,  but,  like  the  feeders, 
have  no  tentacles.  The  medusa- 
buds,  which  are  male  or  female, 
arise  singly,  either  from  the  base 
of  the  reproductive  zooids  or 
from  the  stems  which  unite  the 
latter.  These  buds,  as  in  Tubu- 
lar ia,  wither  without  dropping  from  their  parent  stock.  It 
appears,  then,  that  the  floating  liydrosome  of  a  Siphon- 
ophore  is  like  that  of  the  fixed  Hydr  actinia  or  Coryne,  with 
the  addition  of  locomotive  zooids  and  a  float,  as  seen  in 
PhysaUa,  Vcldla,  or  the  swimming-bells  of  Halistemma. 


Fig.  49. — Fhyvaiia,  or  Portuguese 
man-of-war. — After  Agassi/. 


70  ZOOLOGY. 

The  Siphonophores,  as  observed  in  Agalma,  Epibulia, 
Agalmopsis,  and  other  forms,  arise  from  eggs  which  pass 
through  a  morula,  planula,  and  gastrula  stage.  The  further 
development  of  Agalmopsis  elegans,  a  Siphonophore  native 
to  the  shores  of  New  England,  has  been  described  by  A. 
Agassiz  as  follows  :  In  the  earliest  stage  noticed  the  young 
looked  like  an  oblong  oil -bubble,  with  a  simple  digestive 
cavity.  Soon  between  the  oil-bubble  and  the  cavity  arise  a 
number  of  medusa-buds,  though  without  any  proboscis 
(manubrium),  since  the  medusa-buds  are  destined  to  form 
the  "  swimming-bells,"  which  take  in  and  reject  the  water, 
thus  forcing  the  entire  animal  onward.  After  these  swim- 
ming-bells begin  to  form,  these  kinds  of  Hydra-like  zoo  ids 
arise.  In  one  set  the  Hydra  is  open-mouthed,  and  is,  in 
fact,  a  digestive  tube  ;  its  gastro-vascular  cavity  connecting 
with  that  of  the  stem,  and  thus  the  food  taken  in  is  circu- 
lated throughout  the  community.  These  are  the  so-called 
"  feeders."  The  second  set  of  Hydras  differ  only  from  the 
feeders  in  having  shorter  tentacles  twisted  like  a  corkscrew. 
In  the  third  and  last  set  of  Hydras  the  mouth  is  closed,  and 
they  differ  from  the  others  in  having  a  single  tentacle  in- 
stead of  a  cluster.  Their  function  has  not  yet  been  clearly 
explained.  New  zooids  grow  out  until  a  long  chain  of 
them  is  formed,  which  moves  gracefully  through  the  water, 
with  the  float  uppermost. 

All  the  Hydroids  in  their  free  state  as  medusae  are  more  or 
less  phosphorescent,  and  as  much  or  more  so  after  death, 
when  their  bodies  become  broken  up,  and  the  scattered  frag- 
ments light  up  the  waves  whenever  the  surface  of  the  ocean 
is  agitated.  From  this  cause  the  sea  is  especially  phosphor- 
escent in  August  and  September,  when  the  jelly-fishes  are 
dying  and  disintegrating.  These  creatures  serve  as  food  for 
the  whalebone  whales,  which  swallow  them  by  shoals. 

The  smaller  species  are  abundant  in  the  circumpolar  seas, 
while  in  the  tropics  the  Siphonophores  are  especially  nu- 
merous, none  occurring  in  the  Arctic  regions.  The  Hy- 
droids are  widely  distributed,  a  species  of  Campanularia  be- 
ing common  to  the  Arctic  and  Antarctic  seas.  The  species 
occurring  on  the  New  England  coast  are  in  many  cases 


DISTRIBUTION  OF  HYDROZOA.  71 

found  in  Northern  Europe,  being  circumpolar  in  their  range. 
A  distinct  assemblage  of  Sertularians,  characterized  by  the 
large  number  of  species  of  Plumularia,  inhabits  the  Florida 
seas  down  to  a  depth  of  five  hundred  fathoms.  Among 
the  Discophora  the  Lucernarise  are  arctic  as  well  as  temper- 
ate forms,  while  Cyanea  is  peculiar  to  the  Northern  Hemi- 
sphere. Aurelia  and  Pelagia  are  cosmopolites,  while  Rhaco- 
pilus,  Placo'is,  and  Lobocrocis  are  peculiar  to  the  Southern 
Hemisphere.  The  larger  number  of  species  are  tropical  and 
sub-tropical.  As  regards  their  bathymetrical  distribution, 
while  several  species  extend  to  the  depth  of  five  hundred 
fathoms,  Monocaulus  flourishes  in  gigantic  proportions  at 
the  enormous  depth  of  four  miles. 

The  range  in  geological  time  of  the  Discophora  extends 
to  the  Jurassic  period  (middle  Oolitic),  large  species  of  jelly- 
fishes  occurring  in  the  Solenhofen  slates.  The  genus  Hy- 
dr actinia  first  appeared  in  the  Cretaceous  period.  Grapto- 
lites  were  common  in  the  shales  of  the  Potsdam  period,  so 
that  if  Graptolites  are  Acalephs,  the  latter  are  probably  as 
old  a  type  as  any,  being  contemporaneous  with  trilobites, 
brachiopods,  mollusks,  worms  and  sponges. 


CLASS  I.— THE  HYDROZOA. 

Body  in  its  simplest  form  a  sac  attached  by  tJie  aboral  end,  composed  of 
three  cell-layers,  with  a  mouth  and  gastro-vascular  cavity,  and  in  all  cases, 
except  Protohydra,  provided  with  tentacles,  which  are  hollow,  forming  con- 
tinuations of  the  body -cavity.  The  body  (hydrosome)  usually  differentiated 
into  two  sorts  of  zooids,  nutritive  (polypites)  and  reproductive  (gonosomes\ 
connected  by  a  common  stem  or  nutritive  canal  (cwnosarc),  the  gonosomes 
producing  medusa-buds  (gonopliores),  which  on  being  set  free  are  called  me- 
dusm  (or  medusoids)  and  are  bisexual*  In  these  medusa  the  body  is  disk 
or  bell-shaped,  the  jetty-like  parenchymatous  substance  composing  the  disk 
constituting  the  mesoderm.  From  the  gastro-vascular  cavity  four  primary 
gastro-vascular  canals  radiate  and  anastomose  with  a  marginal  circular 
canal.  No  distinct  organs  of  circulation,  the  blood  being  sea-water  con- 
taining the  chyme  and  a  few  colorless  blood-corpuscles.  A  true  nervous 
system  rarely  present,  but  when  developed  in  certain  medusoids,  forming  a 

*  Agassiz  saw  in  Rhizogeton,  a  form  allied  to  Hydractinia,  a  gonophore  which  had 
discharged  its  contents,  degenerating  into  a  polypite  or  hydra,  and  its  body  elongating 
and  developing  tentacles.  Allman  observed  the  same  thing  in  Cordylophora. 


72  ZOOLOGY. 

thread-ring  around  the  disk,  and  icith  ganglia  near  the  sense-organs.  In 
Hydra  the  nervous  system  is  represented  by  nerw-muscle  cells;  sense- 
organs  usually  present,  represented  by  simple  eyes  and  auditory  vesicles 
(lithocysts),  tlie  two  not  usually  coexisting.  Nettling  organs  (nematocysts) 
usually  present,  and  especially  characteristic  of  the  class,  being  most  abun- 
dant on  the  tentacles. 

The  sexes  rarely  united,  usually  distinct.  Often  a  high  degree  of  poly- 
morphism in  the  individual  hydrosome,  tlie  animal  being  differentiated  not 
only  into  polypltes  and  gonosomes,  but,  in  the  free-swimming  forms,  into 
locomotive  zooids.  Reproduction  takes  place  by  budding,  and  by  fertilized 
eggs  developed  in  glands  attached  to  or  dependent  from  the  primary  ra- 
diating canals.  The  species  undergo  either  a  slight  or  marked  metamor- 
phosis, the  free  gonophores  being  medusa  (or  medusoids),  which  produce 
eggs,  from  which  in  some  Discophora  (such  as  Aurelia}  arise  successively 
a  morula,  gastrula,  planula,  scyphistoma,  strobila,  and  adult  medusa, 
representing  distinct  stages  of  growth. 

Order  1.  Hydroidea.  —  The  individual  either  not  differentiated  into 
zooids,  as  in  Protohydra  and  Hydra,  or  consisting  of  nutri- 
tive and  reproductive  zooids  forming  a  compound,  station- 
ary, branching,  moss- like  body  (hydrosome),  the  medusa- 
buds  remaining  on  the  gonosomes  or  becoming  free  medusa?, 
with  usually  four  simple  radiating  canals,  a  velum,  manu- 
brium,  and  naked  eyes.  Hydrosome  either  naked  or  as  in 
Sertularia,  etc.,  protected  by  a  horny  sheath,  or  forming,  as 
in  Milkpora  and  Heliolites,  a  massive  corallum.  Suborder  1. 
Tubularia(Kydra,  Clava,  Hydractinia,  Millepora.Tubularia). 
Suborder  2.  Campanularim  (Plumularia,  Dynamena,  Cam- 
panularia,  ^quorea,  Zygodactyla). 

Order  2.  Discophora.—  Medusae  like  those  of  the  Hydroids,  but  with 
the  four  primary  radiating  canals  usually  subdividing  into 
numerous  branches,  the  eyes  more  or  less  covered  by  a  flap  ; 
the  velum  often  absent ;  often  four  genital  pouches,  dis- 
charging eggs  into  the  gastro-vascular  cavity  ;  usually  of 
large  size,  and  developing  either  directly  from  eggs,  or,  as 
in  Aurelia,  passing  through  a  gastrula,  scyphistoma,  and 
strobila  stage,  not  being  developed  from  a  hydra-like  poly 
pite.  Suborder  1.  Trachymedusm  (JSgina,  Gunina,  Gery- 
onia,  Charybdsea).  Suborder  2.  Lucernarm  (Lucernaria). 
Suborder  3.  Acale-phce  (Pelagia,  Cyanea,  Aurelia,  Rhizos- 
toma). 

OrderS.  Siphonophora.  —Free-swimming,    polymorphic    hydrosomes, 
with  nutritive,  feeding,  reproductive  and  locomotive  zooids. 
Suborder  1.  Physophora  (Agalma).     2.  Physalm  (Physalia). 
Calycophora  (Diphyes).     4.  Discoidea  (Velella,  Porpita). 


STUDY  OF  HYDROZOA.  73 

NOTE. — Stephanocyphus  mirabilis  Allmari  is  the  type  of  a  new  order 
of  Hydrozoa  called  by  Allman  Thecomedusw.  The  animal  permeates 
and  is  parasitic  in  sponges.  Although  a  Hydrozoan,  it  is  not  a 
Hydroid,  and  cannot  be  referred  to  any  of  the  existing  orders  of  the 
Hydrozoa.  The  chitinous  tubes  which  permeate  the  sponge-tissue  are 
united  toward  the  base  of  the  sponge,  and  constitute  a  colony  of  zooids. 
In  many  respects  it  is  said  to  resemble  the  Campanula?' ice. 

VIEW  OF  THE  CLASSIFICATION  OF  THE  HYDKOZOA. 

Sipkonophora. 
(Physalia.) 


ucopJiora. 

(Aurelia.) 

Hydrc 

(Hyc 

HYDROZOA. 

Laboratory  Work. — The  common  Hydroids,  such  as  Coryne,  Sertu- 
laria,  etc.,  may  be  collected  from  seaweeds  or  the  piles  of  wharves 
between  tide-marks,  while  the  medusae  may  be  obtained  by  the 
hand-net,  or  tow-net  from  a  boat.  The  medusae  especially  abound 
in  eddies  off  points  of  land  where  different  currents  of  the  sea  meet. 
Towing  is  most  effectively  pursued  after  sunset  and  early  in  the  even- 
ing, when  the  sea  is  calm,  and  the  jelly-fish  swim  near  the  surface. 
They  should  be  placed  in  the  jars  by  inverting  the  net  in  the  water  of 
the  jar,  and  examined  at  once,  as  many  will  have  perished  by  the  next 
morning.  Jelly-fish  can  also  be  reared  in  roomy  aquaria,  in  which 
plenty  of  air  is  introduced  by  running  water. 

The  larger  medusae,  such  as  Aurelia,  and  Cyanea,  should  be  sliced 
in  sections  in  order  to  study  their  gross  anatomy,  and  portions  snipped 
off  with  scissors  to  be  examined  with  the  microscope.  The  animals  of 
Sertularians,  Coryne,  etc.,  can  be  studied  alive  in  animalcule-boxes 
and  growing-cells.  The  coral  stock  of  Millepora  was  examined  by 
JVIoseley  in  ground  sections.  "  Portions  of  the  living  coral  were  placed 
in  absolute  alcohol,  chromic  acid,  and  glycerine  ;  portions  were  further 
treated  with  osmic  acid  and  transferred  to  glycerine  or  absolute  alcohol. 
Fragments  of  the  hardened  coral  were  afterward  decalcified  with 
hydrochloric  acid,  and  the  residual  soft  structures  were  either  mounted 
entire  for  examination,  or  cut  in  the  usual  manner  into  fine  vertical 
and  horizontal  sections,  which  were  then  stained  with  carmine  or 
magenta.  The  specimens  hardened  in  osmic  acid,  and  decalcified  after 
subsequent  immersion  in  absolute  alcohol,  yielded  the  best  histological 
results." 


74  ZOOLOGY. 

While  the  jelly-fishes  should  be  studied  alive,  the  larger  ones  can  be 
preserved  in  alcohol,  after  being  killed  b}'  the  gradual  addition  of 
alcohol  to  the  sea-water  in  which  they  are  living.  The  small  medusae, 
as  well  as  Noctiluca  and  the  Ctenophores,  have  been  preserved  with  suc- 
cess by  E.  Van  Beneden,  by  the  use  of  a  solution  of  osmic  acid  or  of 
picric  acid.  Osmic  acid  hardens  the  tissues  so  that  fine  sections  can 
be  made,  and  it  colors  black  the  greasy  matters,  and  especially  myclinc, 
a  chemical  substance  usually  found  in  the  nervous  system,  and  enables 
us  to  trace  well  the  limits  of  the  cells.  The  small  jelly-fishes  may  be 
placed  in  a  very  weak  solution  of  osmic  acid  (^  to  -^  per  cent,  of 
water)  varying  with  the  size  of  the  animal,  for  from  fifteen  to  twenty- 
five  minutes,  when  the  animal  turns  brown.  This  brings  out  clearly 
the  gastro-vascular  canals.  The  specimen  can  then  be  placed  in  strong 
alcohol,  without  losing  its  form  and  transparence.  These  animals  and 
all  other  transparent  animals  can  be  well  kept  in  a  concentrated,  watery 
solution  of  picric  acid.  Professor  Semper  tells  us  that  all  soft  animals, 
worms  as  well  as  hydroids  and  polyps  and  mollusks,  may  be  killed  ex- 
panded in  chromic  acid  (l£  per  cent),  or  in  acetic  acid  of  variable 
strength,  and  then  preserved  in  alcohol. 


CLASS  II.— THE  ACTINOZOA  (Sea-Anemones  and  Coral 
Polyps). 

General  Characters  of  Actinozoans.— So  persistent  is  the 
form  and  structure  of  the  body  in  these  animals,  that  a 
study  of  the  common  sea-anemone  will  enable  the  student 
to  readily  comprehend  the  leading  and  most  fundamental 
characteristics  of  the  class. 

The  common  Actinia  of  our  coast  (Metridium  marginatum} 
is  to  be  found  between  tide-marks  on  rocks  under  sea-weeds, 
or  in  tidal  pools,  but  grows  most  luxuriantly  on  the  piles  of 
bridges.  It  readily  lives  in  aquaria,  where  its  habits  may 
be  studied.  An  aquarium  may  be  improvised  by  using  a 
preserve-jar  or  glass  globe,  covering  the  bottom  with  sand, 
with  a  large  flat  stone  for  the  attachment  of  the  sea-ane- 
mone. By  placing  a  green  sea-weed  (ulva)  attached  to  a 
stone  in  the  jar,  and  filling  it  with  sea-water,  the  animal 
may  be  kept  alive  a  long  time.  After  observing  the  move- 
ments of  the  crown  of  tentacles  as  they  are  thrust  out  or 


O        *'/> 

STRUCTURE  OF  THE  8E A- ANEMONE.  75 

v//5r,     '> 

withdrawn,  specimens  may  be  killed  expanded  by  the^farj- 
ual  introduction  of  fresh  water,  or  by  plunging  them  fntio  / 
picric  acid.  They  should  then  be  transferred  to  the  strong-  • 
est  alcohol,  and  allowed  to  soak  in  it  for  two  or  three  days 
until  the  tissues  become  hard  enough  to  cut  well.  Then 
vertical  and  transverse  sections  may  be  made  with  a  sharp 
knife.  The  first/act  to  observe  is,  that  an  alimentary  canal 
is  much  more  ofearly  indicated  than  in  the  Hydrozoa,  there  - 
being  a  distinct  digestive  sac,  separate  from  the  body-walls, 
hanging  su/pended  from  the  mouth-opening,  and  held  in 
place  by  six  partitions  or  septa  (mesenteries),  which  divide 
the  body-cavity  into  a  number  of  chambers.  The  digestive 
sac  is  not  closed,  but  is  open  at  the  bottom  of  the  body, 
connecting  directly  with  the  chambers,  so  that  the  chyme, 
or  product  of  digestion,  passes  down  to  the  floor  of  the 
body,  and  then  into  each  of  the  chambers ;  thus,  by  the 
movements  of  the  cilia  lining  the  body-cavity,  the  chyme, 
mixed  with  the  blood,  is  distributed  throughout  the  body  ; 
this  rude  mode  of  circulation  being  the  only  means  of  dis- 
tribution of  the  nourishment  contained  in  the  circulating 
fluid,  there  being  no  distinct  canals,  as  in  the  Hydrozoa. 
These  mesenteries  may  be  best  studied  in  a  cross-section  of 
the  animal  after  being  hardened.  It  will  be  found  that 
there  are  six  pairs  of  complete  or  primary  septa  or  partitions 
(mesenteries)  which  hold  the  stomach  in  place,  and  a  num- 
ber of  pairs  of  shorter  ones  of  unequal  length  between  the 
complete  ones.  There  are  never  less  than  twelve  of  the 
secondary  partitions,  even  in  the  young,  and  when  more 
numerous  they  occur  in  multiples  of  six  (Clark).  On  the 
free  edges  of  these  shorter  mesenteries,  which  do  not  extend 
out  to  the  stomach,  there  is  a  mass  of  long  coiled  filaments, 
the  mesenterial  filaments  (craspeda,  Fig.  50,  cr),  which  con- 
tain lasso-cells,  situated  in  a  peripheral  layer,  while  the  fila- 
ment is  hollow  and  contains  guanin.  In  dissecting  the 
sea-anemone  these  mesenterial  filaments  are  always  more 
or  less  in  the  way,  and  have  to  be  carefully  removed  so  as  to 
expose  the  ovaries  and  adjoining  parts.  They  press  out  of 
the  mouth  and  the  cinclides  (small  openings  through  the 


76 


ZOOLOGY. 


body-walls),  not  always  present,  and  end  of  the  tentacles, 
and  thus  come  in  contact  with  animals  forming  their  food. 
The  ovaries  and  spermaries  can  be  distinguished  by  their 
forming  masses  of  closely  convoluted  tubes  much  thicker 
than  the  mesenterial  filaments,  and  situated  on  the  outside 
next  to  the  free  edge  of  each  mesentery  ;  they  are  also  of  a 
pale  lilac  tint  in  Metridium  marginatum  (Fig.  50,  o).  They 
are  not  easily  distinguishable  from  each  other  by  the  naked 
eye.  The  figure  shows  at  the  base  of  the  body  the  free 
edges  of  the  mesenteries  (m)  of  different  heights,  with  the 
spaces  between  them  through  which  the  chyme  passes  into 

the  body-cavity.  For  the  com- 
plete passage  of  the  circulating 
fluid  the  six  primary  mesenteries 
are  perforated  by  a  large  orifice 
(op)  more  or  less  oval  or  kidney- 
shaped  in  outline  (Fig.  50).  The 
digestive  sac  is  divided  into  two 
divisions,  the  mouth  and  stomach 
proper,  the  latter  when  the  ani- 
mal is  contracted  being  much 
shortened,  and  with  the  walls 
vertically  folded,  as  seen  in  the 
cut. 

In  the  tentacles  are  lodged  the 
lasso-cells  or  nematocysts,  and 
the  tentacles  are  hollow,  com- 
municating directly  with  a  cham- 
ber or  space  between  the  mesen- 
teries, and  are  open  at  the  end.  When  a  passing  shrimp, 
small  fish,  or  worm  comes  in  contact  with  these  tentacles, 
the  lasso-cells  are  thrown  out,  the  victim  is  paralyzed,  other 
tentacles  assist  in  dragging  it  into  the  distensible  mouth, 
where  it  is  partly  digested,  and  the  process  is  completed  in 
the  second  or  lower  division  of  the  digestive  canal.  The 
bones,  shells,  or  hard  tegument  of  the  animals  which  may 
be  swallowed  by  the  Actinia  are  rejected  from  the  mouth 
after  the  soft  parts  are  digested.  Pigment-cells,  which  are 


Fig.    50.—  Partly 


diagrammatic 

££*?£ 

LT°r*nmetyntenr!Sgeodr 


d°fJKtogs"y' 


recton 


STRUCTURE  OF  THE  SEA- ANEMONE.  7? 

supposed  to  be  liver-cells,  are  said  to  be  situated  in  the  walls 
of  the  stomach,  and  the  mesenterial  filaments  have  been  sup- 
posed to  act  as  kidneys  in  taking  up  and  excreting  the  waste 
products  of  digestion,  but  this  has  not  been  proved  and  seerns 
improbable.  The  blood,  or  sea-water,  mixed  with  particles 
of  food  ("  chylaqueous  fluid"),  the  result  of  digestion,  was 
supposed  by  Williams  to  represent  the  chyle  of  higher  ani- 
mals and  to  contain  white  blood-corpuscles,  but  this  has 
been  denied  by  Lewes  ("  Sea-side  Studies")  on  apparent  good 
grounds.  Bilateral  or  right  and  left  symmetry  is  faintly  in- 
dicated in  the  young  and  old  Actinia,  as  well  as  in  some 
corals,  as  pointed  out  by  Clark. 

While  no  true  nervous  system  is  known  to  exist  in  the 
Actinozoa,  Duncan  has  discovered  in  flne  base  of  the  body  a 
plexus  of  fusiform  ganglionic  cells  connected  by  nerve-fibres. 
Isolated  nerve-cells  have  been  discovered  by  Schneider  and 
Rotteken  near  the  pigment-cells  or  supposed  eyes  at  the 
base  of  the  tentacles  of  the  Actinia.  In  connection  with 
these  nerve-cells  are  certain  round  refractive  cells  (Haimean 
bodies)  and  other  long  cells,  called  the  Rdttekon  bodies. 
The  former  are  thought  by  Professor  Duncan  to  carry  light 
more  deeply  into  the  tissues  than  the  ordinary  epithelial 
cells.  This  is  also  the  case  with  the  elongated  Rotteken 
cells  and  others  similar  to  them,  called  bacilli.  All  these, 
when  brought  together  in  this  primitive  form  of  eye, 
"concentrate  and  convey  light  with  greater  power,  so 
as  to  enable  it  to  act  more  generally  on  the  nervous  sys- 
tem probably  not  to  enable  the  distinction  of  objects,  but 
to  cause  the  light  to  stimulate  a  rudimentary  nervous  sys- 
tem to  act  in  a  reflex  manner  on  the  muscular  system,  which 
is  highly  developed."  (Duncan.) 

Nearly  all  the  Actinozoa  increase  by  budding,  new  indi- 
viduals arising  at  the  base  or  edge  of  the  pedal  disk  of  the 
old  ones.  Clark  has  seen  in  Metridium  marginatum  as 
many  as  twenty  buds  separate  from  the  parent  sea-anemone. 
"  As  in  Hydra  they  arise  as  simple  rounded  protuberances, 
but  in  a  short  time  six  short  tentacles  make  their  appear- 
ance at  the  free  end,  and  a  minute  oblong  aperture,  the 


78  ZOOLOGY. 

mouth,  is  found  in  their  midst  in  such  a  way  that  its  two 
ends  have  a  tentacle  opposite  each,  and  the  other  four  dis- 
posed two  on  one  side  and  two  on  the  other.  Within,  the 
organs  arise  at  points  corresponding  to  the  position  of  those 
outside.  The  semi-partitions,  twelve  in  number,  begin  as 
mere  ridges,  which  extend  in  pairs  from  the  anterior  end  of 
the  stomach  along  the  oral  wall  toward  its  border."  Adult 
Actiniae  sometimes,  though  rarely,  subdivide  longitudinally, 
but  it  is  not  uncommonly  observed  in  the  corals,  in  which 
cases  only  the  heads  and  stomachs  divide,  the  general  cav- 
ity remaining  common  to  the  two. 

The  development  of  Actinia  meseiribryantliemum  has  been 
traced  by  Lacaze-Duthiers.  The  young  Actinia  attains 
maturity  without  any  metamorphosis.  The  egg  is  supposed 
to  undergo  segmentation  within  the  ovary.  In  the  state  in 
which  the  embryo  was  observed  by  .Lacaze-Duthiers  it  was 
oval  and  surrounded  by  a  dense  coat  of  transparent  conical 
spinules.  Soon  the  two  primitive  germi- 
nal layers  (ectoderm  and  endoderm) 
were  observed.  Two  lobes  next  appear 
within  the  body  ;  these  subdivide  into 
four,  eight,  and  finally  twelve  primitive 
lobes.  This  stage  is  represented  by  the 
corresponding  stage  of  the  coral  (Fig.  55, 
E).  Not  until  after  the  twelve  primitive 
lobes  are  fully  formed  do  the  tentacles 
Fig.  si.- -ciliated  larva  begin  to  make  their  appearance.  When 

(gastrula)  of  a  Polyp,    a,     , ,       ~      .    .        , 

primitive  opening  or  bias-  the  first  twelve  tentacles  have  grown  out, 

topore ;    6,   stomach ;    c,  ,      j>  •  -,  ,  •-, 

ectoderm;  a,  endoderm!  twenty-four  more  arise,  and  so  on,  until 
with  its  increasing  size  the  Actinia  is 
provided  with  the  full  number  peculiar  to  each  species. 
Lacaze-Duthiers  observed  the  same  changes  in  two  species 
of  Sagartia,  and  in  Bunodes  gemmacea.  Fig.  51  represents 
the  ciliated  gastrula  of  an  unknown  polyp  allied  ivKalliphobe. 
While  Metridium  and  Bunodes  are  types  of  the  ordinary 
form  of  Actinoids,  certain  forms,  like  Halcampa  producta 
Stimpson  (Fig.  52),  are  quite  long  and  live  fixed  in  the 
mud  or  sand.  Allied  to  Halcampa  is  Edioardsia,  which 


CORAL  POLYPS. 


79 


lives  in  deeper  water.     Its  young,  however,  is  at  an  early 

stage  of  its  existence  a  free-swimming  polyp,  which  was 

originally  described  as  an  adult  animal  under  the  name  of 

Arachnactis.      In   Zoanthus  the  tegument  is  tough  and 

leathery,    and  the  different  polyps  are  con- 

nected by  stolons.     Epizoantlms  americanus 

Verrill  lives  in  deep  water,  off  the  coast  of 

New  Jersey  and  Southern  New  England,  in 

about  twenty  fathoms.   Cericmthus,  a  gigantic 

form,  a  native  species  of  which  (C.  borealis 

Verrill)  lives  at  the  depth   of  one  hundred 

fathoms  in  the  Gulf  of  Maine  deeply  sunken 

in  the  mud,  where  it  secretes  a  shiny  leathery 

tube,  is  perforated  at  the  end  of  the  body  ; 

the    young    of    a    corresponding    European 

species  is  also  free-swimming,  like  the  young 

Edwardsia. 

The  coral  polyps  differ  from  the  Actinoids 
in  secreting  in  the  mesoderm  a  limestone 
base,  from  which  arise  in  the  Zoantharian 
corals  stony  septa  serving  as  a  support  to  the 
animal  ;  these  septa  are  deposited  or  secreted 
in  the  chambers,  so  that  in  the  coral  polyp 
there  are  soft  partitions  alternating  with  the 
limestone  ones,  the  latter  formed  at  the  base 
of  the  polyp,  not  completely  filling  the  inter-  cama 
mesenterial  chambers. 

Order  1.  Zoantharia.  —  "We  will  now  enumerate  some  of 
the  leading  forms  of  the  first  order  of  Anthozoa,  the  Zoan- 
tliaria,  to  which  the  sea-anemones  and  most  of  the  stony 
corals  belong.  The  group  is  called  by  some  recent  authors 
Hexacoralla,  the  number  of  primary  chambers  and  tenta- 
cles being  six,  the  latter  rounded,  conical,  or  filiform.  In 
the  simple  cup-shaped  corals,  as  Deltocyathus  and  Caryo- 
phyllia,  the  coral  forms  a  cup  or  theca,  the  lamellae  which 
arise  from  the  base  terminate  in  as  many  septa,  the  spaces 
between  which  are  termed  loculi.  A  central  pillar  or  col- 
umn formed  by  the  union  of  the  septa,  or  arising  indepen- 


80  ZOOLOGY. 

dently,  is  called  the  columella,  while  the  small  separate  pillars 
between  the  columella  and  the  septa  are  termed  palulL  In 
the  compound  or  tree-like  corals,  each  young  coral  polyp 
forms  a  calicle,  theca,  or  limestone  support  of  its  own,  which 
unites  with  the  other  by  calcification  of  the  connecting  sub- 
stance of  the  common  body.  This  intermediate  layer  is 
termed  cwnencliyma  (Huxley). 

The  simpler  corals  consist  of  but  a  single  calicle  contain- 
ing one  polyp,  as  in  Flabellum,  Deltocyathus,  and  Caryo- 
pliyllia.  They  live  free,  fixed  in  the  mud  in  deep  water, 
and  occur  in  water  with  a  temperature  of  about  32°  Fahr. 
Flabellum  angular e  Moseley  has  been  dredged  off  Nova 
Scotia  in  1250  fathoms. 

Deltocyathus  Agassizii,  which  is  not  uncommon  in  the 
Florida  channel,  at  depths  varying  from  sixty  to  three  hun- 
dred and  twenty-seven  fathoms,  has  been  dredged  by  us  at  the 
mouth  of  Massachusetts  Bay,  in  one  hundred  and  forty  fath- 
oms (temperature  39°  to  42°  Fahr.).  An  allied  form  is 
UlocyatUus  arcticus  Sars,  said  by  Duncan  to  be  the  same  as 
Flabellum  laciniatum  Edwards  and  Haime,  a  fossil  of  the 
late  tertiary,  dredged  by  us  in  one  hundred  and  fifty  fath- 
oms, near  St.  George's  Banks,  Gulf  of  Maine. 

In  the  family  of  which  Oculina,  the  eye-coral,  is  a  type, 
the  polyp  stock  is  compound,  branched,  increasing  by  lat- 
eral buds.  Lopkohelia  prolifera  Pallas  (Fig.  53)  occurs 
in  the  seas  of  Norway,  and  has  likewise  been  found  to  occur 
on  the  banks  off  Nova  Scotia  and  Newfoundland,  while  it 
lives  in  the  Florida  Straits,  in  from  195  to  315  fathoms. 

In  Mceandrina,  or  the  brain-coral,  Fama,  Astraaantii  As- 
trangia,  we  have  representatives  of  the  important  group 
Astrceacca,  in  which  the  corallum  is  massive,  more  or  less 
hemispherical,  and  the  polyp-cells  or  calicles  are  distinctly 
lamello -radiate  within,  and  generally  so  without.  Budding 
is  usually  carried  on  by  division  of  the  disks,  or  by  spon- 
taneous fission.  In  Mnssa  the  polyps  are  sometimes  two 
inches  in  breadth,  as  large  as  ordinary  Actiniae.  Diploria 
cerebriformis  Edwards  and  Haime  is  a  brain-coral  which  is 
common  in  the  West  Indies  and  at  the  Bermudas,  some- 


CORAL  POLYPS. 


81 


times  growing  to  a  diameter  of  three  feet.     The  common 
large  West  Indian  brain-coral  is  Mceandrina  labyrinth ica. 

In  Astrcea  pallida  Dana,  of  the  Feejee  Islands,  the  polyps 
are  pale,  the  disks  bluish  gray,  and  the  tentacles  whitish. 
The  polyps  of  many  corals  are  beautifully  colored.  Those 


Fig.  53. — Lophohelia  prolifera. — After  Wyville-Thouipsou. 

of  Astrangia  Dana?  Agassiz  are  white.  In  this  coral,  as 
observed  by  Dana,  the  polyps  stand  prominently  above  the 
calicles,  as  only  their  bases  secrete  coral.  The  tentacles 
have  minute  warty  prominences,  each  full  of  lasso-cells. 


b2  ZOOLOGY. 

This  coral  ranges  as  far  north  as  Nantucket  and  Buzzard's 
Bay.  In  the  mushroom  corals,  Fungia,  the  large  coral! urn 
is  the  secretion  of  a  single  polyp  which  may  be  a  foot  in 
length.  Large  branching  corals  abound  on  the  reefs  of 
Florida,  the  most  abundant  of  which  grows  nearly  two  feet 
high  and  branches  out  like  the  horns  of  a- deer.  Such  is 
Madrepora  cervicornis  Lamarck. 

While  agamogenesis  or  alternation  of  generations  is  rare 
among  the  Actinozoa,  Semper  has  observed  two  species  of 
Fungia  which  he  considers  to  reproduce  in  this  way.  The 
corals  "bud  out  from  a  branched  stem,  and  then  become 
detached  and  free,  as  is  the  habit  of  the  genus."  Moseley 


Pig.  54.— Coral  polyp  (Astroides  calyadaris)  expanded.— From  Tenney's  Zoology. 

also  describes  a  similar  case  of  production  of  three  or  four 
generations  in  a  Tahitan  species  of  Fungia. 

As  a  good  example  of  the  mode  of  development  of  one  of 
the  suborder  Madreporaria,  we  will,  with  Lacaze-Duthiers, 
study  the  development  of  Astroides  calycularis  Pallas. 
The  period  of  reproduction  takes  place  between  the  end  of 
May  and  July,  the  young  developing  most  actively  at  the 
end  of  June.  Unlike  Actinia,  which  is  always  hermaphro- 
ditic, this  coral  is  rarely  so,  but  the  polyps  of  different 
branches  belong  to  different  sexes. 

As  in  the  other  polyps,  including  Actinia,  the  eggs  and 


DEVELOPMENT  OF  CORAL  POLYPS. 


83 


spermatic  bodies  rupture  the  walls  of  their  respective  glands 
situated  on  the  fleshy  partitions.  As  in  Actinia,  Lacaze- 
Duthiers  thinks  the  fecundation  of  the  egg  occurs  before  it 
leaves  the  ovary,  when  also  the  segmentation  of  the  yolk 
must  take  place.  Unlike  the  embryo  Actinia,  the  ciliated 
young  of  the  coral,  after  remaining  in  the  digestive  cavity 
for  three  or  four  weeks,  make  their  way  out  into  the  world 
through  the  tentacles.  The  appearance  of  the  young,  when 
first  observed,  was  like  that  in  Fig.  55,  A,  being  an  oval, 
ciliated  gastrula  with  a  small  mouth  and  a  digestive  cavity. 

The  gastrula  changes  into   an   actinoid   polyp  in   from 
thirty  to  forty  days  in  confinement,  after  exclusion  from  the 
parent,  but  in  nature  in  a 
less  time,   and  it  probably 
does  not  usually  leave  the 
mother   until    ready  to   fix 
itself  to  the  bottom. 

Before  the  embryo  be- 
comes fixed  and  the  tentacles 
arise,  the  lime  destined  to 
form  the  partitions  begins 
to  be  deposited  in  the  endo- 
derm.  Fig.  55,  (?,  shows  the 
twelve  rudimentary  septa. 
These  after  the  young  polyp 
or  "  actinula"  has  become 


Fig.  55.— Development  of  a  coral  polyp, 
Astroid  s  calycularis.   A ,  ciliated  pastrula ; 


stationary,     finally     enlarge 

and   become   -joined   to   the  ^y°»"g  p°]yp  with  i2iBepta;""cT3T  young 

_,  J  polyp  farther  advanced,  with  12 tentacles; 

external    Walls   OI    the    COral    <?,  the  corallum  and  limestone  septa  begin- 
„    „  . .          ning  to  form.— After  Lacaze-Duthiers. 

now  in  course  of  formation 

(Fig.  55,  C,  c),  forming  a  groundwork  or  pedestal  on  which 
the  actinula  rests.  D  represents  the  young  polyp  resting 
on  the  limestone  pedestal. 

Lacaze-Duthiers  found  that  the  embryo  polyp  which  had 
been  swimming  about  in  his  jars  for  nearly  a  month,  sud- 
denly, within  the  space  of  three  or  four  hours  after  a  hot 
sirocco  had  been  blowing  foi*  three  days,  assumed  the  form 
of  small  disks  (Fig.  55,  B],  divided,  as  in  the  Actinia,  into 
twelve  small  folds  forming  the  bases  of  the  partitions  within. 


84  ZOOLOG  Y. 

The  tentacles  next  arise,  being  the  elongation  of  the 
chambers  between  the  partitions,  six  larger  and  elevated, 
six  smaller  and  depressed  (Fig.  55,  />).  The  definitive  form 
of  the  coral  polyp  is  now  assumed,  and  in  the  Astroides  it 
becomes  a  compound  polypary. 

There  are  but  few  facts  regarding  the  rate  of  growth  of 
corals.  Pourtales  states  that  a  specimen  of  Mcsandrina 
labyrinthica,  measuring  a  foot  in  diameter  and  four  inches 
thick  in  the  most  convex  part,  was  taken  from  a  block  of 
concrete  at  Fort  Jefferson,  Tortugas,  which  had  been  in  the 
water  only  twenty  years.  Major  E.  B.  Hunt  calculated 
that  the  average  growth  of  a  Maeandrina  observed  by  him 
at  Key  West  was  half  an  inch  a  year.  From  the  observa- 
tions and  specimens  collected  by  Mr.  J.  A.  Whipple,  as 
stated  by  Verrill,  a  Madrepora  found  growing  on  the  wreck 

of  the  Severn  grew 
to  a  height  of  sixteen 
feet  in  sixty-four 

1  ^^^     Jears>  or  a^  the  rate 

>^l\f^^    of     three    inches    a 
year. 

The  group  Rugosa 
o  f      Milne-Edwards 

Pig.  56.— a,  Haplophyllia  paradoxa  ;  b,  vertical  sec-    n n A    TTo imo  nrmfaina 
tion ;  c,  calicle  from  above. -After  Pourtales. 

a    large   number   of 

palaeozoic  corals,  which  are  mainly  characterized  by  having 
four  primary  septa,  the  number  in  most  living  corals  being- 
six  ;  and  also  by  intracalicinal  gemmation,  which  also  occurs 
in  a  few  Caryop^yllids  and  Oculinids. 

Pourtales  has  doubtfully  referred  to  this  group  his  Haplo- 
phyllia paradoxa  (Fig.  56)  which  inhabits  the  Florida 
Straits  at  a  depth  of  over  three  hundred  fathoms.  The 
nearest  known  fossil  ally  of  this  interesting  coral  is  Calo- 
pliyllum  profundum  Germ.,  which  is  fossil  in  the  Dyas  for- 
mation. Duncan  describes  Guynia  annulata,  another  deep- 
sea  coral,  as  a  recent  Rugose  tetrameral  coral.  Moseley 
suggests  from  a  study  of  Heliopora,  together  with  Crypto- 
helia  and  other  StylasteridcB,  that  "  the  marked  tetrameral 
arrangement  of  the  septa  in  Rugosa,  and  the  presence  in 


ALCTONARIAN  POLYPS.  85 

many  forms  of  tabula?,  are  certainly  characters  not  opposed 
to  the  alliance  of  these  corals  with  the  Alcyonarians,"  and 
gives  other  reasons  of  importance  in  favor  of  this  view. 

The  group  of  Antipathea,  represented  by  Antipathes  ar- 
borea  Dana,  of  the  Feejee  Islands,  produce  compound 
groups  by  budding,  growing  in  the  form  of  delicate  shrubs. 
The  polyps  have  usually  six  tentacles,  though  in  Gerardia 
they  have  twenty-four. 

Order  2.  Alcyonaria. — To  this  group  of  polyps,  which 
have  eight  serrated  or  feathered  tentacles,  belong  the  red 
coral  of  commerce,  the  sea-fans  and  sea-pens,  in  which  there 
are  no  calcareous  septa,  and  in  which  the  corallum  has,  as  in 
the  sea-fans  and  sea-pens,  a  bony  axis,  while  the  flesh}'  por- 
tion (coenosarc)  represents  the  mesoderm  and  is  filled  with 
calcareous  spicules. 

In  the  genera  Haimea,  Alcyonium,  Tubipora,  etc.,  the 
polyps  are  encrusting,  budding  out  in  different  ways,  and 
adhere  to  foreign  bodies  by  the  coenenchyma.  ffaimea  is 
simple,  consisting  of  but  a  single  polyp.  In  Alcyonium 
the  coenenchym  is  much  developed,  soft,  lobulated,  and 
branching.  Our  common  species  is  A.  car  mum  Agassiz. 
In  Tubipora  the  polyps  are  compound  and  secrete  solid 
calcareous,  bright  red  tubes,  arranged  side  by  side,  like  the 
pipes  of  an  organ,  and  supported  by  horizontal  plates. 

In '  the  common  red  coral  (Corallium  rubrum)  of  the 
Mediterranean  Sea,  the  solid,  unjointed  coral-stock  consists 
of  a  crystalline  basal  mass,  with  calcareous  spicules  solidly 
united.  The  bright  red  coral  is  worked  into  various  orna- 
ments. The  coral  fishery  is  pursued  on  the  coasts  of  Algiers 
and  Tunis,  where  assemble  in  the  winter  ai.d  spring  from 
two  hundred  to  three  hundred  vessels.  The  coral-fishermen, 
with  large  rude  nets,  break  off  the  coral  from  the  submerged 
rocks.  About  half  a  million  dollars'  worth  of  coral  is  annu- 
ally gathered. 

Heliopora,  now  proved  by  Mr.  H.  N.  Moseley  to  be  an 
Alcyonarian  instead  of  an  Actinoid  polyp,  differs  from 
Corallium  and  Tubipora  "in  that  the  hard  tissue  of  its 
corallum  shows  no  signs  of  being  composed  of  fused  spic- 
ules." This  genus,  together  with  Polytremacis  and  the 


86  ZOOLOGY. 

Silurian  Heliolites,  form,  according  to  Moseley,  a  new 
family  of  Alcyonarians  in  which  the  corallum  consists  of  an 
abundant  tubular  coerienchym,  with  calicles  having  an 
irregular  number  of  pseudo-septa,  which  do  not,  however, 
correspond  with  the  membranous  mesenteries.  The  polyps 
are  completely  retractile,  with  the  tentacles  when  retracted 
introverted.  The  mouths  of  the  sacs  lining  the  crenenchy- 
mal  tubes  are  closed  with  a  layer  of  soft  tissue,  but  com- 
municate with  one  another  and  with  the  calicular  cavities 
by  a  system  of  transverse  canals  (Moseley).  Heliopora  cceru- 
lea  grows  on  coral  reefs  at  the  Philippine  Islands  and  at 
Singapore. 

In  the  family  of  sea-fans  (Goryonidce)  the  coral-stock  is 
horny  or  calcareous,  branching  tree-like,  or  forming  a  flat 
network.  The  short  calicles  of  the  single  retractile  polyps 
stand  perpendicularly  to  the  axis,  communicating  by  longi- 
tudinal vessels  and  branching  canals.  Gorgonia  (Rliipigor- 
gia)  fiabellum  Linn,  is  red  or  yellow  and  abundant  on  the 
Florida  reefs.  In  the  Arctic  seas  and  the  deeper,  colder 
waters  of  the  Newfoundland  Banks  and  St.  George's  Banks, 
Primnoa  reseda  (Pallas)  and  Paragorgia  arborea  (Linn.) 
grow  ;  the  latter  being  of  great  size,  the  stem  as  thick 
through  as  one's  wrist,  and  the  whole  corallum  over  five  feet 
in  height. 

In  the  family  of  sea-pens  (PennatuUdce)  the  polyp-stock 
is  free,  growing  in  the  sand  or  mud,  usually  with  a  bony 
axis  supporting  the  polyps,  and  capable  of  moving  at  the 
base.  In  Pennatula,  or  the  sea-pen,  there  are  secondary 
branches  in  which  the  polyps  are  situated  ;  this  polyp  is 
phosphorescent  ;  one  species  (P.  aculeata  Danielssen)  lives 
in  deep  water.  An  Arctic  form,  Umbellularia  groenlandica, 
is  a  gigantic  form,  growing  about  four  feet  high,  in  from 
three  hundred  to  two  thousand  fathoms.  The  species  of 
Emilia  are  kidney-shaped,  with  the  polyps  placed  on  one 
side.  Renilla  reniformis  Cuvier  is  a  rich  purple  species, 
occurrinr  i  the  sand  at  Charleston,  S.  C.  According  to 
Agassiz,  this  animal  is  remarkably  phosphorescent,  emitting 
"  a  golden  green  light  of  a  most  wonderful  softness." 

While  coral  reefs  are  in  part  composed  of  Alcyonarians, 


FORMATION  OF  CORAL  REEFS. 


87 


Polyzoa,  and  certain  plants  called  Nullipores,  the  Madrepo- 
raria  in  the  main  are  the  true  reef -builders.  They  are  con- 
fined to  waters  in  which  through  the  coldest  winter  month 
the  temperature  of  the  water 
does  not  fall  below  68°  F., 
though  usually  the  waters  are 
much  warmer  than  this,  the 
mean  annual  temperature  be- 
ing  about  73  J°  F.  in  the  North 
Pacific  and  70°  F.  in  the 
South.  Coral  reefs  are  abun- 
dant  in  the  West  Indies,  but 
still  more  so  in  the  Central 
Pacific,  where  there  are  a 
much  greater  number  of  spe- 
cies  of  corals  (Dana).  Along 
the  Brazilian  coast,  as  far 
south  as  Cape  Frio,  are  coral 
reefs  (Hartt).  In  depth  living 
coral-reef-builders  do  not  ex- 
tend  more  than  fifteen  or 
twenty  fathoms  below  the  sur-  |' 
face. 

Coral  reefs  are  divided  by  | 
Dana  into  outer  or  barrier 
reefs  (Fig.  57)  and  inner  reefs. 
The  barrier  reefs  are  formed 
from  the  growth  of  corals  ex- 
posed  to  the  open  seas,  while 
the  inner  or  fringing  reefs 
(Fig.  57)  are  formed  in  quiet 
water  between  a  barrier  reef  ? 
and  the  island.  As  coral 
reefs  are  usually  built  upon 
islands  which  are  slowly  sink- 
ing, barrier  reefs  are  simply 
ancient  fringing  reefs  formed  when  the  island  stood  higher 
above  the  sea,  hence  they  are  built  up  as  rapidly  as  the  land 
sinks,  and  thus  the  top  of  the  reef  kc-^s  at  the  level  of 


88 


ZOOLOGY. 


the  sea.  The  reefs  are  often  of  great  thickness,  for,  as 
Dana  says,  "  could  we  raise  one  of  these  coral-bound  islands 
from  the  waves,  we  should  find  that  the  reefs  stand  upon 


the  submarine  slopes,  like  massy  structures  of  artificial 
masonry ;  some  forming  a  broad  flat  platform  or  shelf 
ranging  around  the  land,  and  others  encircling  it  like  vast 


FORMATION  OF  CORAL  REEFS.  89 

ramparts,  perhaps  a  hundred  miles  or  more  in  circuit." 
Darwin  has  estimated  that  some  reefs  in  the  Pacific  Ocean 
are  at  least  2000  feet  in  thickness. 

Thus  far  we  have  spoken  of  reefs  surrounding  mountainous 
islands  ;  coral  islands  or  atolls  (Fig.  58)  resemble  such  reefs, 
except  that  they  surround  a  lake  or  lagoon  instead  of  a  high 
island,  the  coral  island  itself  being  seldom  more  than  ten  or 
twelve  feet  above  the  sea,  and  usually  supporting  a  growth  of 
cocoanut  trees,  while  the  sea  maybe  of  great  depth  very  near 
the  outer  edge  of  the  atoll,  which  "  usually  seems  to  stand  as 
if  stilted  up  in  a  fathomless  sea  "  (Dana).  These  reefs  and 
atolls  are  formed  and  raised  above  the  sea  by  the  action  of 
the  winds  and  waves,  in  breaking  up  the  living  corals, 
comminuting  it  and  forming  with  the  debris  of  shells  and 
other  limestone-secreting  animals  and  plants,  banks  or  de- 
posits of  coral  mixed  with  a  chalky  limestone,  as  the  base  of 
the  reef.  When  it  rises  above  the  waves,  cocoanuts  and  other 
seeds  are  caught  and  washed  up  on  the  top,  and  gradually 
the  island  becomes  large  enough  to  support  a  few  human 
beings.  The  Bermudas  are  the  remnants  of  a  single  atoll, 
and  are  situated  farther  from  the  equator  than  any  other 
reefs.  Most  barrier  reefs  and  coral  islands  or  atolls  are 
formed  in  an  area  of  subsidence,  where  the  bottom  of  the 
ocean  is  gradually  sinking  ;  this  accounts  for  the  peculiar 
form  and  great  thickness  of  many  reefs.  On  the  other 
hand,  the  coral  reefs  of  the  West  Indies  are,  generally 
speaking,  in  an  area  of  elevation. 

A  section  of  a  coral  reef  is  shown  by  Fig.  59:  n  is  the  point 
where  the  shore  slopes  rapidly  down  within  the  lagoon 
(which  lies  to  the  right),  and  m  is  where  the  reef  suddenly 
descends  toward  the  open  ocean.  Between  b  c  and  d  e  lies 
the  higher  part  of  the  reef.  The  shore  toward  the  lagoon 
slopes  away  regularly  from  d  to  n  ;  while  toward  the  open 
ocean  there  is  a  broad  horizontal  terrace  (a  to  ~b  c)  which 
becomes  uncovered  at  low  water. 

The  theory  of  the  formation  of  barrier  reefs  is  shown  by 
the  diagram,  Fig.  60.  The  island,  for  example,  the  volcanic 
island  Coro,  which  is  slowly  sinking,  at  the  ancient  sea-level 
I  is  surrounded  by  a  fringing  reef  //,  a  small  rock-terraco 


90  ZOOLOGY  „ 

at  the  former  level  of  the  sea.  Where  the  island  has  sunk  to 
the  level  of  the  water-line  II,  the  reef  appears  at  the  sur- 
face as  at  V  f,  I  f.  There  is  now  a  fringing  and  a  barrier 
reef,  with  a  narrow  canal  between  them  ;  V  is  a  section  of 
the  barrier  reef,  e'  of  the  canal  or  lagoon,  and  /'  of  the 
fringing  reef.  After  a  farther  submergence  to  the  sea-level 
III,  the  canal  e"  becomes  much  wider.  On  one  side  (//) 
the  reef  is  present,  on  the  other  side  it  has  disappeared,  ow- 
ing to  the  agency  of  ocean-currents.  Finally,  at  the  water- 
level  IV,  there  are  two  small  islands  surrounded  by  a  wide 
lagoon,  with  two  reef-islets  i'",  i'",  resting  upon  two  sub- 
marine peaks.  The  coral  reef  has  now  grown  to  great  di- 
mensions, and  covered  almost  the  entire  original  island, 
and  though  the  reef -building  coral  polyps  cannot  live  below 


Fig.  60.— Schematic  section  of  an  island  with  reefs. 

a  point  fifteen  or  twenty  fathoms  below  the  surface,  yet  ow- 
ing to  the  slow  sinking  of  the  island,  they  build  up  the 
reef  as  rapidly  as  the  former  subsides,  and  in  this  way  after 
many  centuries  a  coral  reef  sometimes  two  thousand  'feet 
thick  may  be  built  up  in  mid-ocean. 

Coral  reefs  are  mainly  confined  to  the  Western  and  Cen- 
tral Pacific  and  the  Indian  Oceans,  and  to  the  Caribbean 
Sea.  None  occur  on  the  west  coast  of  North  America  or  of 
Africa,  and  only  limited  patches  on  the  eastern  coast  of 
South  America.  There  were  palaeozoic  reefs,  such  as  the 
fossil  coral  reef  extending  across  the  Ohio  River  at  Louis- 
ville. 


ACTINOZOA.  91 

CLASS  II.— THE  ACTINOZOA. 

Ccdenterates  icith  a  digestive  sac  partially  free  from  the  "body-cavity  open- 
ing  into  it  below  and  held  in  place  by  six  or  eight  mesenteries  radiating  from 
the  digestive  cavity  and  dividing  the  perivisceral  space  into  chambers.  Mouth 
surrounded  with  a  circle  of  tentacles,  which  are  hollow,  communicating  di- 
rectly with  the  perivisceral  chambers.  A  slightly  marked  bilateral  symmetry. 
To  the  edges  oftfw  mesenteries  (usually  the  free  ones)  are  attached  the  repro- 
ductive glands,  both  male  and  female,  or  of  one  sex  alone  ;  also  the  craspeda, 
or  mesentenal  filaments,  wJiich  contain  a  large  number  of  lasso-cells.  Body 
either  entirely  fleshy,  or  secreting  a  calcareous  or  horny  coral-stock,  and 
wlien  the  species  is  social  connected  by  a  cwnenchyme.  In  some  forms  (sea- 
pens)  the  entire  colony  capable  of  limited  locomotion.  No  well-marked 
nervous  system,  but  a  plexus  of  fusiform  ganglionic  cells  connected  by  nerve- 
fibres  in  the  base  of  Actinians.  Reproduction  by  self  division,  gemmation, 
or  by  ova,  the  sexes  being  separate  or  united  in  the  same  individual;  tlie 
young  undergoing  a  morula  and  gastrula  condition,  and  then  becoming 


Order  1.  Zoantharia. — Mesenteries  and  tentacles  usually  six  or  in  mul- 
tiples of  six,  corallum  with  calcareous  septa.  Mesenterial  fila- 
ments abundantly  developed  (Astrsea,  Madrepora,  Actinia). 

Oi'der  2.  Alcyonaria. — Mesenteries  and  tentacles  always  eight  in  num- 
ber. Coral-stock  without  true  septa.  Mesenterial  fila- 
ments not  usually  numerous.  Corallum  usually  horny,  and 
the  whole  colony  in  the  Pennatulacea  capable  of  locomo- 
tion (Alcyonium,  Gorgonia,  Pennatula,  Renilla). 

VIEW  OF  THE  CLASSIFICATION  OF  THE  ACTINOZOA. 

Alcyonaria. 
(Alcyonium.) 

Zoantharia. 
(Actinia.) 


ACTINOZOA. 

Laboratory  Work. — Verrill  has  preserved  Actiniae  completely  ex- 
panded by  slowly  adding  a  saturated  solution  of  picric  acid  to  a  small 
quantity  of  sea-water  in  which  they  had  expanded.  "When  dead  they 
should  be  transferred  to  a  pure  saturated  solution  of  the  acid,  and 
allowed  to  remain  for  from  one  to  three  hours,  according  to  size,  etc. 
They  should  then  be  placed  in  alcohol,  which  should  after  a  day  or  two 
be  renewed.  Thus  hardened  they  can  be  cut  into  sections.  Corals 
can  be  studied  by  grinding  or  sawing  sections,  and,  if  desirable,  treated 
as  in  the  case  of  the  corallum  of  the  Millepores. 


ZOOLOGY. 


CLASS  III. — CTENOPHORA  (Comb-bearers). 

General  Characters  of  Ctenophores.— These  beautiful  an- 
imals derive  their  name  Ctenopliora,  or  "  comb-bearers/' 
from  the  vertical  rows  of  comb-like  paddles  (ctenophores) 
situated  on  meridional  bands  of  muscles  which  serve  as  lo- 
comotive organs,  the  body  not  contracting  and  dilating  as 
in  the  true  jelly-fishes.  In  their  organization  they  are 
more  complicated  than  the  Actinozoa,  as  they  have  a  true 
digestive  cavity  passing  through  the  body- cavity,  with  two 
posterior  outlets  (it  will  be  remembered 
that  Cerianthus  has  one  at  the  end  of 
the  body).  From  this  alimentary  canal 
are  sent  off  chymiferous  or  water- vascu- 
lar canals  (Fig.  61)  which  correspond  in 
their  mode  of  origin  with  the  water- 
tubes  of  the  Echinoderms.  As  regards 
the  rows  of  paddles,  each  vertical  row 
consists  of  a  great  number  of  isolated, 
transverse,  comb-like  fringes  placed  one 
above  the  other,  and  movable,  either 
isolately  or  in  regular  succession  or 
simultaneously  (Agassiz).  As  these  rows 
of  paddles  are  connected  for  their  whole 

Fig.  61. -view  of  the   length  with  a  chymiferous  tube,   they 
gastro-vascniarcanaisofa   probably  aid  in  respiration.     These  ani- 

Pleuroorachia,  from  which  ,,  n  i    i  •    i         • 

the  two  retractile  arms   mals  also  stand  much  higher  in  the  scale 

have   been  removed.     A,        „   ,.„       .,  ,,  ,,          ^     -,       ,         ,         , 

from  one  side,  the  mouth-   of  life  than  the  other  Ccelenterates  by 

opening   above ;  B,   seen    ••  ITI-IJ.        ixi  TI 

from  the  mouth-end.—  being  more  truly  bilateral,  the  radial 
symmetry  so  marked  in  the  Actinia  or 
in  the  jelly-fish  being  in  these  animals  less  apparent,  as  the 
parts  are  developed  on  opposite  sides  of  a  median  plane. 
The  nervous  system,  as  originally  described  by  Grant,  con- 
sists of  a  ganglion  situated  at  the  aboral  end  (end  opposite 
to  the  mouth)  of  the  Pleurobrachia,  from  which,  among 
other  nerves,  eight  principal  ones  are  distributed  to  the 
eighf,  rows  of  paddles.  A  nerve  also  proceeds  to  the  so- 
called  otolitic  sac  (lithocyst)  seated  upon  the  ganglion. 
Eimer  has  lately  shown  that  the  nervous  system  of  the 


AFFINITIES  OF  CTEWOPHOHKS.  93 

Ctenophora,  as,  for  example,  that  of  Beroe,  agrees  in  general 
with  that  of  the  jelly-fishes,  with  the  difference  that  in  the 
Ctenophores  the  nerve-centres  are  not  situated  on  the  edge, 
but  at  the  pole  of  the  body  opposite  the  mouth.  On  the 
other  hand,  the  nervous  system  is  not  radiated  as  in  th'e 
jelly-fishes  or  as  in  the  Echinoderms. 

Our  commonest  example  of  this  class  is  the  Pleurobrachia 
rhododacyla  Agassiz.  It  is  a  beautiful  animated  ball  of 
transparent  jelly  moving  through  the  water  by  means  of 
eight  rows  of  minute  paddles,  throwing  out  from  a  sac  on 
each  side  of  the  body  two  long  ciliated  tentacles.  It  is 
abundant  in  autumn  ;  sometimes  thousands  may  be  seen 
stranded  on  the  shore  at  low  water. 

That  the  Ctenophores  have  affinities  to  the  sea-anemones 
(Actinozoa)  is  seen  in  the  form  and  relations  of  the  diges- 
tive tract,  though  it  differs  in  hanging  free,  not  being  held 
in  place  by  radiating  mesenteries,  and  in  this  respect  they 
approach  the  Echinoderms.  From  their  possessing  a  dis- 
tinct digestive  tract,  the  Ctenophores  need  not  be  confounded 
with  the  jelly-fishes  (Hydrozoa}.  On  the  other  hand,  they 
present  some  advance  over  the  Actinozoa,  and  in  some 
respects  connect  the  Hydrozoa  and  Actinozoa  with  the 
Echinoderms.  For  example,  the  water-vascular  system 
arises  in  the  Ctenophores  as  outgrowths  from  the  digestive 
sac,  as  they  do  in  the  young  star-fish  and  sea-urchins.  This 
indicates  that  in  the  mode  of  development  of  both  the  di- 
gestive tract  and  the  water- vascular  system  the  Ctenophores 
are  allied  to  the  Echinoderms  rather  than  to  the  Hydrozoa, 
in  which  the  water- vascular  tubes  arise  as  simple  hollows  in 
the  body-mass.  Moreover,  they  are  less  radiated  than  in 
the  Hydrozoa  or  Echinoderms. 

In  Bolivia  alata  Agassiz  the  body  is  plainly  bilateral  and 
the  water- vascular  tubes  are  very  distinct.  In  Idyia  roseola 
Agassiz  the  mouth  is  large,  the  stomach  wide,  and  the 
body  is  of  an  intense  roseate  hue.  This  beautiful  species  after 
death,  late  in  summer,  is  very  phosphorescent ;  all  Cteno- 
phores, however,  even  their  eggs  and  embryos,  are  phospho- 
rescent. In  the  Ctenophores  the  ovaries  and  spermaries  occur 
in  the  same  individual  and  form  blind  sacs  attached  to  the 


94  ZOOLOGY. 

water- vascular  tubes,  and  are  developed  locally,  as  in  Cesium, 
or  along  the  whole  length  of  the  tubes,  the  sexually-differ- 
ent glands  being  placed  in  Beroe  and  allies  on  opposite 
sides  of  the  tube. 

When  ripe  the  eggs  pass  into  the  perivisceral  space,  and 
finally  pass  out  through  the  openings  of  the  body.  The 
eggs  of  Pleurobrachia  escape  singly  ;  in  Bolina  they  are 
laid  in  strings,  while  those  of  Idyia  are  deposited  in  a  thick 
slimy  mass.  They  spawn  late  in  the  summer  and  in  the 
autumn.  The  young  develop  in  the  autumn,  becoming 
nearly  mature  in  the  following  spring.  Development  is  di- 
rect, the  young  hatching  nearly  with  the  form  of  the  adult, 
there  being  no  metamorphosis. 

The  species  are  widely  distributed,  a  number  being  com- 
mon to  both  sides  of  the  Atlantic,  and  the  same  species,  ap- 
parently, of  Pleurobrachia  and  Idyia  occur  on  the  east  and 
west  coast  of  North  America.  The-  most  widely  distributed 
forms  are  the  Beroids.  While  the  genus  Mertensia  is  en- 
tirely arctic,  the  larger  number  of  species  are  either  tropi- 
cal or  subtropical.  The  classification  of  the  group  is  shown 
in  the  following  summary. 


CLASS  III.— CTENOPHORA. 

Spherical  or  oval,  somewhat  bilateral,  scarcely  radiated  animals,  with 
jelly-like,  transparent  bodies.  The  digestive  tract  opens  at  the  posterior 
end  into  the  perivisceral  cavity ;  from  the  canal  pass  off  eight  water-vas- 
cular tubes,  which  are  in  close  relation  with  eight  vertical  meridional  series 
of  comb-like  locomotive  organs.  Usually  a  pair  of  tentacles,  which  may 
become  withdrawn  into  sacs,  and  are  provided  with  thickset  lasso- cells  on 
the  tentacular  fringes.  Nervous  system  consisting  of  an  aboral  ganglion, 
sending  off  eight  nervous  filaments  to  each  of  the  eight  rows  of  paddles. 
The  sexual  glands  seated  in  the  same  individual.  No  metamorphosis, 
tJie  young  when  hatched  resembling  the  adult. 

Order  1.  EurystomecB. — Body  oval,  with  a  large  mouth  and  capacious 
stomach.  The  water-vascular  tubes  connected  with  the 
ctenophores,  and  forming  numerous  ramifications,  commu- 
nicating by  means  of  a  circular  canal  near  the  mouth 
(Beroe,  Idyia). 


CLASSIFICATION  OF  CTENOPHORES. 


95 


Order  2.  Saccatce. — Body  more  or  less  spherical,  with  two  long  tenta- 
cles capable  of  being  wholly  retracted  in  a  sac  (Pleuro- 
brachia). 

Order  3.  T&niata. — Body  ribbon-like,  being  very  much  compressed  in 
the  direction  of  the  lateral  diameter  (Cestum). 

Order  4.  Lobatce. — Body  lateral,  compressed,  bilobed  (Bolina). 


VIEW  OF  THE  CLASSIFICATION  OF  THE  CTENOPHOKA. 

Lobata. 
(Boliua.) 


T&niata. 
(Cestum.) 


Saccata. 

(Pleurobrachia.) 


Eurystomeas. 
(Idyia.) 


CTENOPHOKA. 

Laboratory  Work.  — The  Ctenophorse  should  be  studied  while  alive. 
They  may  be  collected  with  a  drag  or  tow-net  from  a  boat  when  the 
surface  of  the  ocean  is  calm.  For  studying  the  fine  anatomy  and 
tissues  they  should  be  treated  by  the  same  methods  as  the  smaller  jelly- 
fishes. 


'  '>  It  A  /; 


CHAPTER  IV. 

BKANCH   IV.— ECHINODERMATA  (STAR-FISH,   SEA- 
URCHINS,  SEA-CUCUMBERS,  ETC.) 

General  Characters  of  Echinoderms.— We  now  come  to 
animals  of  much  more  complicated  structure  than  any  of 
the  foregoing  branches,  and  in  which  the  radiated  arrange- 
ment of  the  parts  of  the  body  is  in  most  cases  as  marked 
as  the  jointed  or  ringed  structure  of  worms  or  insects  ;  for 
not  only  are  the  body- walls  of  the  star-fish  or  sea-urchin,  or 
even  many  of  the  Holothurians  (though  less  plainly),  di- 
vided into  five  wedge-shaped  portions  (splieromeres),  or  pro- 
duced into  five  arms  as  in  the  common  star-fish  or  five- 
finger,  but  the  nervous  system,  the  reproductive  organs, 
the  blood  and  water-vascular  systems,  and  the  locomotive 
appendages  of  the  latter,  are  usually  arranged  in  accordance 
with  the  externally  radiated  form  of  the  body.  Still  these 
animals  are  in  many  cases,  as  in  the  higher  sea-urchins, 
plainly  bilateral,  while  in  the  larval  forms  of  all  Echino- 
derms whose  development  is  known  the  young  are  not 
radiated,  but  more  or  less  bilateral,  as  in  the  larvae  of  worms 
and  mollusks.  The  most  trenchant  character,  however, 
separating  the  Echinoderms  from  the  Coelenterates,  and  ally- 
ing them  to  the  worms,  is  the  genuine  tube-like  digestive 
canal  which  lies  free  in  the  body-cavity  (peri  visceral  cavity), 
and  may  be  several  or  many  times  the  length  of  the  body. 

The  student  can  gain  a  correct  idea  of  the  general  struc- 
ture of  the  Echinoderms  from  a  careful  examination  of  the 
common  star-fish  (Asterias  vulgaris  Stimpson),  which  is  the 
most  common  and  accessible  Echinoderm  to  be  found  on  the 
New  England  shores.  After  placing  a  star-fish  in  some  sea- 
water  and  noticing  its  motions,  the  thrusting  out  of  the  am- 
bulacral  feet  or  suckers  by  which  it  pulls  or  warps  its  clumsy 


STRUCTURE  OF  COMMON  STAR-FISH.  97 

body  over  the  mussel-beds,  or  rocks,  or  weeds,  the  arms 
being  capable  of  slightly  bending  ;  after  observing  the  red 
eye-spot  at  the  end  of  each  arm  or  ray,  and  the  movements 
of  the  numerous  spines  which  are  attached  to  the  separate 
plates  forming  the  calcareous  framework  of  the  body- 
walls,  and  examining  the  movements  of  certain  modified 
spines  called  pedicellarice,  which  are  pincer-like  bodies  situ- 
ated among  the  spines,  the  student  will  be  ready  to  study 
the  external  and  internal  anatomy. 

First,  as  to  the  calcareous  framework  of  the  star-fish. 
In  order  to  study  this,  a  transverse  section  should  be  made 
through  an  arm,  and  a  vertical  one  through  the  body  and 
along  the  middle  of  a  single  arm,  and  finally  the  animal 
should  be  divided  into  two  halves,  an  -upper  and  lower.  It 
will  then  be  seen  that  the  calcareous  framework  or  so-called 
skeleton  consists  of  a  great  number  of  limestone  plates  or 
pieces  attached  by  a  tough  membrane  and  covered  by  the 
skin.  Between  the  plates  are  spaces  by  which  the  water  enters 
the  body-cavity  through  the  skin.  These  plates  are  arranged 
so  as  to  give  the  greatest  strength  and  lightness  to  the  body. 
There  is  also  to  be  seen  an  oral  (actinal)  side  on  which  the 
mouth  is  situated,  and  an  aboral  (abactinal)  side,  the  re- 
spective limits  of  which  areas  vary  greatly  in  the  different 
groups  of  Echinoderms.  Each  arm  or  ray  is  deeply  chan- 
nelled by  the  ambulacral  furrow  containing  four  rows  of 
suckers  or  "ambulacral  feet,"  which  are  tentacle-like 
protrusions  of  the  skin  growing  out  through  orifices  in 
the  ambulacral  plates,  and  are  a  continuation  of  the  water- 
sacs  or  "  ampullae  "  within.  The  madreporic  plate  is  a 
flattened  hemispherical  body  situated  on  the  disk  between 
two  of  the  arms.  It  is  perforated  by  canals. 

We  are  ROW  ready  to  examine  the  internal  organs  and  to 
study  their  relations  to  one  another  and  to  the  body-walls. 
The  nervous  system  may  be  seen  without  dissection.  By 
closely  examining  the  mouth  a  pentagonal  ring  is  seen  sur- 
rounding it,  each  angle  slightly  enlarging*  and  sending  off 

*  Owfsiannikoff  states  that  the  nervous  ring  is  a  flat  band,  con- 
taining no  swellings  or  ganglia,  and  not  differing  in  structure  from  the 
ambulacral  nerves,  which  latter  possess  nerve-cells  as  well  as  fibres. 


98 


ZOOLOGY. 


a  nervous  cord  to  the  eye  at  the  end  of  the  ray.  It  may  be 
discovered  by  pressing  apart  the  ambulacral  feet  along  the 
median  line  of  each  arm.  Fine  nerves  are  sent  off  to  each 
sucker,  passing  through  the  opening  between  the  calcareous 
plates  and  extending  to  each  ampulla,  thus  controlling  the 
movements  of  the  ambulacral  feet. 


Fig.  62.— Longitudinal  section  through  the  body  and  one  arm  of  Asterias  vulgaris. 
m,  mouth;  s,  stomach;  I,  lobe  of  stomach  extending  into  the  arm;  a,  anus  ;  nr,  ner- 
vous ring  ;  n,  radial  nerve ;  vr,  water- vascular  ring,  sending  a  radial  vessel  (v)  into  the 
arm  ;  mp,  madreporic  plate  ;  t ,  stone  canal ;  h,  haemal  canal ;  ov,  oviduct ;  o,  ovary  ; 
am,  ampullae,  the  ambulacral  feet  projecting  below ;  b,  cceca  or  liver. — Drawn  by 
A.  F.  Gray,  under  author's  direction. 

The  mouth  (Fig.  62,  m)  is  capacious,  opening  by  a  short 
oesophagus  into  a  capacious  stomach  (Fig.  62,  s)  with  thin 
distensible  walls,  and  sending  a  long  lobe  or  sac  (Fig.  62,  /) 
into  the  base  of  each  arm  ;  each  sac  is  bound  down  by  two 
retractor  muscles  attached  to  the  median  ridge  lying  be- 
tween the  two  rows  of  water-sacs  (ampullae,  see  also  Fig.  63). 


Fig.  63.— Diagram  of  the  cross-section  of  an  arm.    A,  of  Asterias  rubens ;  B.  of 
opfiiura  texturata  ;  »,  ambulacral  feet ;  j?',  ampullae .;  t,  dermal  tentacles  ;  w,  nervous 
ords  •  w,  ambulacral  plates  ;  w,  muscles  ;  a,  ambulacral  vein  ;  b,  ventral  plate  ;  c,  tot- 
al plates;  d,  dorsal  plate  ;  &,  calcified  portion  of  the  integument.— After  W  Lance 
from  Gegenbaur. 

The  stomach  ends  in  a  short  intestine,  the  limits  between 
the  two  not  distinctly  seen.  The  intestine  suddenly  con- 
tracts and  ends  in  a  minute  rectum  situated  in  an  angle 
between  two  of  five  fleshy  ridges  radiating  from  the  centre 


STRUCTURE  OF  COMMON  STAR-FISH.  99 

of  the  aboral  disk.  The  anus  (Fig.  62,  a)  is  minute  and 
difficult  to  detect,  being  situated  between  the  short  spines, 
and  is  evidently  not  used  in  the  expulsion  of  faecal  matter 
unless  the  urinary  secretions,  if  there  be  such,  pass  out  of 
it.  Tt  would  seem  as  if  the  opening  were  rudimentary  and 
that  the  star-fish  had  descended  from  Echinoderms  like  the 
Crinoids,  in  which  there  is  a  well-marked  external  terminal 
opening  of  the  digestive  tract.  Appended  to  the  intestine 
are  the  "  coeca  "  or  "  liver  "  (Fig.  62,  1],  consisting  of  two 
long,  tree-like  masses  formed  of  dense  branches  of  from 
four  to  six  pear-shaped  follicles,  connecting  by  a  short  duct 
with  the  main  stem.  The  two  main  ducts  unite  to  form  a 
short  common  opening  into  the  intestine.  The  coaca  are 
usually  dark,  livid  green,  and  secrete  a  bitter  digestive 
fluid,  representing  probably  the  bile  of  the  higher  animals. 

The  star-fish  is  bisexual,  but  the  reproductive  glands  are 
much  alike,  the  sexes  only  being  distinguishable  by  a  micro- 
scopic examination  of  the  glands.  The  ovaries  (Fig.  62,  o) 
are  long  racemose  bodies  lying  along  each  side  of  the  in- 
terior of  the  arms,  and  the  eggs  are  said  to  pass  out  by  a 
short  narrow  oviduct  (ov)  through  an  opening  between  two 
plates  on  each  side  of  the  base  of  the  arms,  the  opening  be- 
ing small  and  difficult  to  detect. 

The  water-vascular  system  consists  of  the  madreporic 
body,  the  "  stone-canal "  (Fig.  62,  t),  the  ring  or  circumoral 
canal  (vr),  and  the  radial  vessels  (v)  ending  in  the  water- 
sacs  (am)  and  ambulacral  feet.  The  stone-canal  begins 
at  the  outer  and  under  side  of  the  sieve-like  madreporic 
body,  passing  directly  forward  and  downward  in  a  sinuous 
course  to  the  under  side  of  the  circumoral  plates.  The 
madreporic  body  (mb)  is  externally  seen  to  be  perforated  by 
linear  apertures  radiating  and  subdividing  toward  the  pe- 
riphery. The  sea-water  in  part  enters  the  body-cavity 
through  the  fissures  in  the  madreporic  body,  while  most  of 
it  enters  the  stone-canal,  which  is  a  slender  tube  scarcely 
one  fourth  the  diameter  of  the  entire  madreporic  body. 
The  water  entering  the  stone-canal  (Fig.  62,  t)  passes  di- 
rectly into  the  water- vascular  ring  (Fig.  62)  and  then  into 
the  ten  Polian  vesicles  and  the  five  radial  canals,  whence 


100  ZOOLOGY. 

it  is  conveyed  to  each  water-sac  or  ampulla  (Fig.  62,  am). 
These  pear-shaped  water-sacs,  when  contracted,  are  supposed 
to  press  the  water  into  the  long  slender  suckers  or  ambulacral 
feet,  which  are  distended,  elongated,  and  by  a  sucker-like  ar- 
rangement at  the  end  of  the  prehensile  foot  act  in  conjunc- 
tion with  the  others  to  warp  or  pull  the  star-fish  along. 
Besides  locomotion  the  ambulacral  feet  serve  for  respiration 
and  perception  (Simroth).  Hoffman  shows  that  the  feet 
of  the  sea-urchins  can  be  projected  or  thrust  out  without 
the  aid  of  the  ampullae. 

It  will  thus  be  seen  that  the  water-vascular  system  in  the 
star-fish  is  in  its  functions  partly  respiratory  and  partly 
locomotive,  while  it  is  in  connection  with  the  vascular  sys- 
tem, and  thus  partly  aids  in  circulating  the  blood  and 
chyle. 

Of  the  true  vascular  or  blood  system  the  student  can  ordi- 
narily only  discover  one  portion,  the  so-called  "  heart"  or 
"  pulsating  vessel,"  which  we  may  call  the  haemal  canal  (Fig. 
62  h),  and  which  runs  parallel  to  the  stone-canal  from  the 
madreporic  body  to  near  the  ring-canal.*  It  is  nearly  as 
large  as  the  stone-canal,  slightly  sinuous,  muscular,  and  with 
the  latter  is  surrounded  by  a  loose  investing  membrane  like 
a  pericardium.  Some  observers  deny  the  existence  of  a  vas- 
cular (sometimes  called  "  pseudohaemal  ")  system,  but  it  has 
been  recently  studied  by  Hoffman  and  subsequently  by  Teu- 
scher,  who  maintains  that  in  all  Echinoderms  there  are  two 
systems  of  blood-vessels,  which  belong,  one  to  the  viscera  and 
the  other  to  the  nervous  system,  forming  an  oral  or  nervous 
ring  and  an  anal  ring.  The  two  rings  are  in  direct  com- 
munication in  the  star-fishes,  Ophiurans  and  sea-urchins, 
but  not  in  the  Holothurians.  The  radial  nerves  are  ac- 
companied by  a  vessel  which  subdivides  and  distributes 
branches  to  the  ambulacral  feet  in  star-fishes,  Echini,  and 
Holothurians.  Teuscher  considers  that  the  "  heart  "  found 
in  the  star-fishes  and  Echini  connecting  the  cesophageal  (or 
nerve-ring)  and  anal  ring,  is  neither  a  gland  nor  a  pulsating 
vessel,  as  different  authors  have  supposed,  but  perhaps  only 

*  Simroth  states  that  in  Ophiurans  (Ophiactis)  the  stone-canal  opens 
in  common  with  the  "  heart"  into  the  madreporic  plate. 


CRIN01DS.  101 

a  relict  of  an  earlier  period  of  development.  In  the  Ophi- 
urans  the  oral  canal  opens  directly  into  the  body-cavity  ; 
in  Ectiinotlirix  directly  connects  with  the  outer  world  by 
means  of  the  interradial  canals.  Finally,  he  regards  the 
nervous  vessel  as  homologous  with  the  ventral  vessel  of  the 
worms. 

Having  made  ourselves  acquainted  with  the  general  struc- 
ture of  the  Echinoderms  as  exemplified  in  the  star-fish,  we 
are  prepared  to  study  the  modifications  of  the  Echinoderm 
plan  in  the  different  classes. 


CLASS  I. — CRINOIDEA  (Stone-lilies,  Encrinites,  etc.) 

Order  1.  Bracliiata. — The  living  representatives  of  those 
Crinoids  which  lived  in  palaeozoic  and  early  mesozoic 
times  are  few  in  number,  and  for  the  most  part  live  in  deep 
water,  or,  as  in  the  case  of  Rhizocrinus  and  its  living  allies, 
at  great  depths.  They  are  like  Limulus  and  Nebalia,  rem- 
nants of  an  ancient  fauna.  There  are  but  eight  genera 
known — viz.,  Holopus,  Rhizocrinus ,  Bathycrinus,  Hyocri- 
nus,  Pentacrinus,  Comaster,  Actinometra,  and  Antedon 
(Comatuld).  Of  the  first  five  genera  the  species  are  attached 
by  a  stalk  to  the  sea-bottom,  while  the  last  three  genera  are 
in  their  young  state  stalked,  but  finally  become  detached. 
The  body  or  calyx  divides  into  arms  bearing pinnulce  or  sub- 
branches. 

The  Pentacrinus  lives  attached  to  rocks  from  twenty  to 
thirty  fathoms  below  low-water  mark  in  the  West  Indies. 
The  stem  is  about  a  foot  long,  the  joints  pentagonal,  send- 
ing oif  at  intervals  whorls  of  unbranched  cirri.  "  No  dis- 
tinct basal  piece  is  known,  but  the  calyx  appears  to  begin 
with  the  first  five  radialia  "  (Huxley).  Pentacrinus  ca- 
put-meduscB  Miiller  (Fig.  64)  and  P.  Mulleri  Oersted  are 
West  Indian  species.  P.  Wyville-Thompsoni  Jeffreys  was 
dredged  in  deep  water  on  the  coast  of  Portugal.  In  the 
fossil  P.  sulangularis  the  stalk  was  more  than  fifty  feet  long. 
Bathycrinus  gracilis  Wyville-Thompson  is  closely  allied 


102 


ZOOLOGY. 


to  Rhizocrinus,  and  was  dredged  in  the  Bay  of  Biscay  o. 
the  depth  of  2435  fathoms.  B.  Aldrichianus  occurred  in 
1850  fathoms,  latitude  1°  47'  X.,  longitude  24°  26'  W.,  off 
the  coast  of  Brazil.  With  it  and  also  near  the  Crozet 
Islands  occurred  the  interesting  Hyocrinus  BetJiellianus 
AVyville-Thompson,  which  bears  in  some  points  resemblance 
to  the  palaeozoic  genus,  Platycrinus. 


Fig.  64.— a,  Pentacrinm  cajwt-medusce,  half  natural  size:  b  calyx-disk  seen  from 
above,  natural  size.-^From  Brehm's  Thierleben. 

The  most  widely  distributed  species  is  the  Rhizocrinus 
lofotensis  of  Sars  (Fig.  65),  which  is  closely  related  to  the 
Bourguetticrinus  of  the  chalk  formation,  and  forms  the 
transitional  type  connecting  the  ApiocrinidcB  with  the 
free-moving,  unstalked  Antedon.  It  occurs  at  the  depth  of 


STRUCTURE  OF  CRINOIDS. 


103 


from  one  hundred  to 
one  thousand  fathoms 
in  the  North  Atlantic 
and     Floridan    seas, 
and  is  a  characteristic 
member  of  the  abyssal 
fauna.     This  crinoid 
consists  of  a  jointed 
stalk,    a    cup -shaped 
body    (calyx),     from 
the    edge    of    which 
from    five    to    seven 
(the  number   varies) 
arms  (bracliia)  radi- 
ate, which  subdivide 
into  a   double   alter- 
nate   series    of  pin- 
nulce.    The  mouth  is 
situated  in  the  centre, 
while  the  anus  is  situ- 
ated on  a  conical  pro- 
jection on  one  side  of 
the  oral  disk,  between 
the  bases   of  two  of 
the  arms.     R.  Raw- 
soni  Pourtales  occurs 
in  from  eighty  to  one 
hundred  and  twenty 
fathoms     at    Barba- 
does. 

In  Holopus,  a  short, 
stout  form  with  no 
true  sfcalk,  but  at- 
tached  by  a  broad  en- 
crusting base,  there 
are  ten  arms  originat- 
ing from  five  axial 
joints.  "  When  con- 
tracted  the  arms  are 


104  ZOOLOGY. 

rolled  in  a  spiral  and  press  laterally  against  one  another  so 
as  to  enclose  a  hermetically  closed  cavity."  The  pinnules 
are  formed  of  broad  flat  joints,  and  are  "  rolled  spirally  to- 
ward the  ambulacral  channel  of  the  arms  when  contracted" 
(Pourtales).  The  only  species  yet  known  is  H.  Rangii 
D'Orbigny,  from  Barbadoes. 

In  Antedon  (Comatula)  the  body  is  at  first  stalked,  but 
afterward  drops  off,  when  it  represents  the  calyx  and  arms 
of  the  ordinary  Crinoids.  It  thus  passes  through  a  Rhizo- 
crinus  condition,  showing  that  it  is  a  higher,  more  recent 
form.  The  mouth  opens  into  a  short,  broad  oesophagus, 
and  a  wide  stomach  which  makes  a  turn  and  a  half,  ending 
in  the  anal  cone  placed  between  the  base  of  two  of  the  arms. 
Within  the  five  triangular  plates  is  a  circle  of  tentacles. 
From  the  space  between  each  pair  of  oral  plates  the  ambu- 
lacral grooves  radiate  to  the  arms  and  their  branches.  H. 
Ludwig  maintains  that  Antedon  possesses  a  true  water- vas- 
cular system  formed  on  the  typical  Echinoderm  plan  ; 
there  being  a  ring-canal,  with  radial  vessels  arising  from  it. 
The  tentacles  of  the  perisome  are  connected  with  the  ring- 
canal,  and  the  tentacles  of  the  arms  and  pinnulae  are  con- 
nected with  the  radial  vessel.  Ludwig  has  also  discovered 
in  Antedon  a  system  of  blood-vessels  ("  pseudo -haemal " 
system)  consisting  of  an  oral  ring-canal  and  five  vessels 
radiating  from  it,  which  send  branches  to  the  tentacles,  as 
in  Asterias.  He  also  detected  a  "  dorsal  organ,"  which 
he,  contrary  to  Perrier  and  P.  H.  Carpenter,  considers  to 
be  the  central  organ  of  the  whole  system  of  blood-vessels. 
Both  Ludwig  and  Carpenter,  however,  regard  it  as  homolo- 
gous with  the  so-called  "  heart  "  or  haemal  canal  of  Echini 
and  Asterias. 

The  nervous  system  consists  of  an  oral  ring  with  branches 
extending  into  the  arms. 

The  body-cavity  extends  into  the  arms,  and  the  ovaries 
for  the  most  part  lie  in  the  cavity  of  the  arms,  as  in  Asterias. 

The  internal  anatomy  of  Rhizocrinus  has  been  investi- 
gated by  Ludwig,  who  finds  that  it  agrees  very  closely  with 
that  of  Antedon.  The  water-vascular  system,  nervous  sys- 
tem, alimentary  canal  and  its  appendages,  have  the  same 


DEVELOPMENT  OF  CRINOIDS. 


105 


relations  as  in  the  unstalked  Crinoids  (Antedon  and  Actin- 
ometrd),  only  they  are  on  a  simpler  plan,  there  being  a 
close  similarity  between  RMzocrinus  and  the  pentacrinoid 
stage  of  Antedon. 

The  ovaries  of  Antedon  open  externally  on  the  pinnules 
of  the  arms,  while  there  is  no  special  opening  for  the  prod- 
ucts of  the  male  glands,  and  Thompson  thinks  that  the 
spermatic  particles  are  "  discharged  by  the  thinning  away 
and  dehiscence  of  the  integument."  The  ripe  eggs  hang 
for  three  or  four  days  from  the  opening  like  a  bunch  of 
grapes,  and  it  is  during  this  time  that  they  are  fertilized. 
The  following  account  is  taken  (sometimes  word  for  word) 


Pig.  66.—  Development    of  a  Crinoid  (Antedon).    A,  morala;  B,  free  larva,  with 
bands  of  cilia;  C,  young  crinoid.—  After  Wyville-Thompson. 


from  "VVyville-Thompson's  researches  on  Antedon  rosaceus 
(Fig.  G?)  of  the  European  seas.  In  the  first  stage  the  egg 
undergoes  total  segmentation  (Fig.  66).  A  represents  the 
egg  with  four  nucleated  cells,  an  early  phase  of  the  mul- 
berry or  morula  stage.  After  the  process  of  segmentation 
of  the  yolk  is  finished,  the  cells  become  fused  together  into 
a  mass  of  indifferent  protoplasm,  with  no  trace  of  organiza- 
tion, but  with  a  few  fat  cells  in  the  centre.  This  pro- 
toplasmic layer  becomes  converted  into  an  oval  embryo, 
whose  surface  is  uniformly  ciliated.  The  mouth  is  formed 
with  the  large  cilia  around  it  before  the  embryo  leaves  the 


10G 


ZOOLOGY. 


egg.  When  hatched,  the  larva  is  long,  oval,  and  girded 
with  four  zones  of  cilia,  with  a  tuft  of  cilia  at  the  end,  a 
mouth  and  anal-opening,  and  is  about  eight  millimetres 
long.  The  body-cavity  is  formed  by  an  inversion  of  the 
primitive  layer  which  seems  to  correspond  to  the  ectoderm. 
Within  a  few  hours  or  sometimes  days,  there  are  indica- 
tions of  the  calcareous  areolated  plates  forming  the  cup  of 
the  future  crinoid.  Soon  others  appear  forming  a  sort  of 
trellis-work  of  plates,  and  gradually  build  up  the  stalk,  and 
lastly  appears  the  cribriform  basal  plate.  Fig.  66,  B,  c,  rep- 
resents the  young  crinoid  in  the  middle  of  the  larva,  whose 
body  is  somewhat  compressed  under  the  covering-glass. 


Fig.  67.—  Antedon,  stalked  and  free.— From  Macallieter. 

Next  appears  a  hollow  sheath  of  parallel  calcareous  rods, 
bound,  as  it  were,  in  the  centre  by  the  calcareous  plates. 
This  stalk  (B,  c)  arises  on  one  side  of  the  digestive  cavity 
of  the  larva,  and  there  is  no  connection  between  the  body- 
cavity  of  the  larva  and  that  of  the  embryo  crinoid. 

Two  or  three  days  after  the  appearance  of  the  plates  of 
the  crinoid,  the  larva  begins  to  change  its  form.  The 
mouth  and  digestive  cavity  disappear,  not  being  converted 
into  those  of  the  crinoid.  The  larva  sinks  to  the  bottom, 
there  resting  on  a  sea- weed  or  stone,  to  which  it  finally  ad- 
heres. The  Pentacrinus  form  is  embedded  in  the  larval  body 


FOSSIL  CRINOIDS.  107 

(the  cilia  having  disappeared),  now  constituting  a  layer  of 
protoplasm  conforming  to  the  outline  of  the  Antedon. 

Meanwhile  the  cup  of  the  crinoid  has  been  forming.  It 
then  assumes  the  shape  of  an  open  bell ;  the  mouth  is 
formed,  and  five  lobes  arise  from  the  edges  of  the  calyx. 
Afterward  five  or  more,  usually  fifteen  tentacles,  grow  out, 
and  the  young  Antedon  appears,  as  in  Fig.  66,  C.  The 
walls  of  the  stomach  then  separate  from  the  body- walls. 
The  animal  now  begins  to  represent  the  primary  stalked 
stage  of  the  Orinoids,  that  which  is  the  permanent  stage  in 
RMzocrinus,  Pentacrinus,  and  their  fossil  allies.  After  liv- 
ing attached  for  a  while  (Fig.  67),  it  becomes  free  (see  right- 
hand  figure)  and  moves  about  over  the  sea-bottom. 


Pig.  68.— A  Blastoid,  Pentremites,  seen  from  the  side  aiid  from  above.— After  Liitken. 

There  are  two  species  of  Antedon  on  the  New  England 
coast,  one  (A.  Sarsii)  inhabiting  deep  water  in  about  one 
hundred  fathoms,  and  the  other  (A.  Esclirichtii  Miiller) 
shallower  water  (twenty-five  fathoms)  in  the  Gulf  of  Maine. 

Order  2.  Blastoidea. — No  forms  have  been  discovered 
later  than  the  Carboniferous  period.  The  group  began 
its  existence  as  species  of  Pentremites  (Fig.  68)  in  the 
Upper  Silurian,  and  culminated  in  the  Carboniferous  age. 
It  connects  the  Crinoids  with  the  Cystideans  ;  the  species 
have  no  arms,  are  supported  on  a  short,  jointed  stalk,  and 
the  oral  plates,  when  closed,  as  they  are  in  a  fossil  state, 
make  the  calyx  look  like  a"  flower-bud.  There  is  a  mouth 
and  eccentric  anal  outlet  and  five  radiating  grooves,  along 


108 


ZOOLOGY. 


each  side  of  which  are  attached  a  row  of  pinnules.  Be- 
sides Pentremites  are  the  typical  genera  Elceacrinus  and 
Eleatherocrinus. 

Order  3.  Cystidece. — This  group  is  likewise  extinct.  In 
the  fossil  Pseudocrinus  there  is  a  short- join  ted  stalk,  while 
in  Caryocystites  (Fig.  69)  there  is  no  stalk  and  no  arms,  the 


Fig.  69.—  Caryocys- 
tites, a  Cystidean.— 
After  Lutkeu. 


Fig.  71. — Agelacrinus,  a  Cystidean,  on 
the  shell  of  a  Brachiopod.—  After  Liitkeu 


Fig.  70.— Pseudocri- 
nus, a  Cystidean.— 
After  Lutkeu. 


body  being  angulo-spherical,  composed  of  solid  plates.  The 
Cystideans  (Figs.  69  to  71)  originated  in  the  Cambrian  for- 
mation, attained  their  maximum  development  in  a  number 
of  species  in  the  Silurian,  and  became  mostly  extinct  in  the 
Carboniferous  period. 


CLASS  I.— CRINOIDEA. 

Spherical  or  cup-shaped  Echinoderms,  without  a  madreporic  plate,  usu- 
ally attached,  by  a  jointed  stem,  a  few  free  in  adult  life,  with  five  arms  sub- 
dividing into  pinnuloB;  the  ambulacral  feet  in  the  form  of  tentacles 
arising  around  the  mouth  in  the  furrows  of  the  calyx  or  situated  on  tJie 
jointed  arms.  In  the  Blastoidea  and  certain  Cystideans  the  arms  are  ab- 
sent, but  the  pinnulce  are  usually  present,  though  absent  in  Caryocystites. 
Circulatory,  water-vascular,  and  sexual  organs  much  as  in  other  Echino- 
derms ;  the  digestive  canal  ending  in  a  distinct  eccentric  aperture. 


GENERAL   STRUCTURE  OF  STAR-FISHES.         109 

Order  1.  BracMita  (True  Crinoids). — Calyx  with  large  pinnulated 
arms,  without  dorsal  calical  pores,  mostly  stalked  (Encri- 
nus,  Pentacrinus,  Apiocrinus,  Rhizocrinus,  Holopus,  Ante- 
doii,  Actinometra,  Phanogenia). 

Order  2.  Blastoidea. — Armless,  but  with  five  series  of  pinnulas,  and 
with  a  stalk  (Pentremites.  No  living  representatives). 

Order  3.  Oygtidea.—'JJsaaSlj  armed,  with  jointed  pinnulae,  and  a  short 
stalk,  the  latter  sometimes  absent,  as  in  Caryocystites.  (All 
fossil  forms,  as  Edriaster,  Caryocystites,  Sphaeronites,  etc.) 

Laboratory  Work. — The  living  Crinoids  are  great  rarities,  and  few 
students  have  access  even  to  alcoholic  specimens.  The  recent  re- 
searches on  their  internal  anatomy  have  been  made  in  large  part  by 
cutting  thin  sections  for  the  microscope,  and  staining  them  with  car- 
mine, etc.,  after  the  methods  of  the  histologist. 


CLASS  II. — ASTEROIDEA  (Star-fishes). 

General  Characters  of  Star-fishes.  —  Having  already 
studied  the  structure  of  the  common  star-fish,  we  are  pre- 
pared to  understand  the  classification  of  the  class.  The 
star-fishes  have  star-shaped,  flattened  bodies,  with  round  or 
flattened  arms,  a  madreporic  plate,  and  two  or  four  rows  of 
ambulacral  feet. 

Order  1.  OpMuridea  (Sand-Stars). — This  division  is 
characterized  by  the  body  forming  a  flattened  disk,  with 
cylindrical  arms,  the  stomach  not  extending  into  the  arms, 
and  there  is  no  intestine  or  anal  opening.  The  ambulacral 
furrow  is  covered  by  the  ventral  shields  of  the  tegument,  so 
that  the  ambulacral  feet  project  from  the  sides  of  the  arm. 
They  have  no  interambulacral  spaces  or  plates.  The  am- 
bulacral feet  or  tentacles  do  not  have  a  sucker  at  the  end, 
but  are  provided  with  minute  tubercles.  They  move  faster 
than  the  true  star-fishes,  the  arms  being  more  slender  and 
flexible.  The  madreporic  body  is  one  of  the  large  circular 
plates  in  the  interambulacral  spaces  around  the  mouth. 
The  external  openings  for  the  exit  of  the  eggs  form  distinct 
fissures  or  slits,  one  on  each  side  of  each  arm.  The  ovaries 
arc  situated  in  the  body,  not  extending  into  the  arms,  the 


110  ZOOLOGY. 

eggs  being  expelled  into  the  perivisceral  cavity,  and  thence 
finding  their  way  out  into  the  water  through  the  interradial 
slits.*  The  Ophiurans  are  bisexual,  but  one  species  being 
known  to  be  unisexual,  viz.,  Ophiolepis  squamata,  accord- 
ing to  Metsclmikoff.  While  most  Ophiurans  pass  through 
a  metamorphosis,  the  young  of  Ophiolepis  ciliata  is  developed 
within  the  body  of  the  parent,  adhering  by  a  sort  of  stalk 
(Krohn).  In  Ophiopliolis  bellis  development  is  direct,  there 
being  no  metamorphosis. 

An  Ophiuran  which  has  accidentally  lost  its  arms  can  re- 
produce them  by  budding.  Ltttken  has  discovered  that  in 
species  of  Opliiothela  and  Opliiactis  the  body  divides  in  two 
spontaneously,  having  three  arms  on  one  side  and  three  on 
the  other,  while  the  disk  looks  as  if  it  had  been  cut  in  two 
by  a  knife  and  three  new  arms  had  then  grown  out  from 
the  cut  side.  Simroth  has  made  farther  extended  researches 
on  self-fission  in  Opliiactis. 

The  Ophiurans  in  most  cases  undergo  a  decided  meta- 
morphosis like  that  of  the  star-fish,  which  will  be  described 
at  length  farther  on.  The  larva,  called  a  pluteus,  is  free- 
swimming,  though  in  some  species  the  young,  in  a  modified 
larval  condition,  reside  in  a  pouch  situated  above  the  mouth 
of  the  parent,  finally  escaping  and  swimming  freely  about 
(A.  Agassiz). 

In  Ophiocoma  vivipara  Ljungman,  which  occurs  in  the 
South  Atlantic,  the  young  at  first  live  in  the  body  of  the 
parent  and  afterward  cluster  on  the  surface  of  her  disk. 
The  eggs  are  hatched  successively,  the  young  being  found 
in  a  regularly  gradated  series  of  stages  of  growth  (Wyville- 
Thompson).  It  appears  probable,  as  in  the  case  of  the  sea- 
urchins,  that  the  Ophiurans  of  the  cooler  portions  of  the 
South  Atlantic,  in  most  cases  at  least,  have  no  metamor- 
phosis. Several  native  forms  are  also  viviparous. 

Our  most  common  sand-star  is  Opliiopliolis  bellis  Lyman 
(Fig.  72),  which  may  be  found  at  low-water  mark,  and  espe- 
cially among  the  roots  of  Laminaria  thrown  up  on  the 

*  On  the  other  hand,  Ludwig  denies  that  the  eggs  pass  into  the  peri- 
visceral  cavity,  but  insists  that  they  collect  in  pouches  formed  by  an  in- 
troversion of  the  integument. 


SAND-STARS  AND  STAR-FISHES. 


Ill 


beacli.  It  is  variable  in  color,  but  beautifully  spotted  with 
pale-and  brown,  its  general  hue  being  a  brick-red.  Am- 
phiura  squamata  Sars  has  long  slender  arms  and  is 
white  ;  it  lives  below  tide-marks.  The  basket-fish,  me- 
dusa's head,  or  Astrophyton 
Agassizii  Stm.,  is  of  large 
size,  the  disk  being  two  in- 
ches across,  and  the  arms 
subdividing  into  a  great 
number  of  tendril-like 
branches.  It  lives  from  ten 
to  one  hundred  fathoms  in 
the  Gulf  of  Maine. 

Ophiurans  are  widely  dis- 
tributed, and  live  at  depths 
between  low- water  mark  and 
two  thousand  fathoms.  Fos- 
sil Ophiurans  do  not  occur 
in  formations  older  than  the  Upper  Silurian,  where  they  are 
represented  by  the  genera  Protaster,  Palceodiscus,  Acroura, 
and  Eucladia  ;  genuine  forms  closely  like  those  now  living 
appear  in  the  muschelkalk  beds  of  Europe  (Middle  Trias). 

Order  2.  Asteridea. — In  the  true  star-fishes  the  arms  are 
direct  prolongations  of  the   disk,  and  the   stomach  and 


Fig.  IZ.—OphiopJiolisbellis,  common  Sand- 
star. — After  Morse. 


Pig.  73.— Three  forma  of  Star-fish,  A,  B,  C,  seen  from  above,  showing  the  different 
development  of  the  ambulacral  and  interarnbulacral  areas.  The  ambulacra  are  indi- 
cated by  rows  of  dots ;  o,  mouth;  r,  arms ;  ir,  iutermdial  or  interambulacral  areas. 
C  Pteraster;  B,  Goniodiscus;  A,  Astei-iscus.— After  Gegenbaur. 

ovaries  or  spermaries  project  into  them,  and  there  is  a  deep 
ambulacral  furrow,  while  the  interambulacral  spaces  vary 
much  in  development  (Fig.  73) ;  the  feet  are  provided  with 


118 


ZOOLOGY. 


suckers,  excepting  those  at  the  end  of  the  arms,  which  are 
tentacle-like.  We  have  already  described  the  commonv star- 
fish of  our  north-eastern  coast,  Aster ias  Forbesli  of  Desor 
(Pig.  74).  This  and  the  allied  varieties  are  abundant  on 
mussel  and  oyster  beds,  being  very  injurious  to  the  latter, 
which  serve  them  as  food.  The  star-fish  projects  its  capa- 
cious stomach,  turning  it  inside  out,  between  the  open 
valves  of  the  oyster,  and  sucks  in  the  soft  parts,  in  this  way 
doing  much  damage  to  the  oyster-beds  of  the  southern  coast 
of  New  England. 


Fig.  74.-Asterias  Forbesii,  natural  size.— After  A.  Agassiz. 

The  bodies  of  star-fishes  as  well  as  sea-urchins  (Echini) 
are  covered  with  pedicellarioe,  which  in  the  former  are  situ- 
ated around  the  base  of  the  spines  on  the  upper  side  of  the 
body.  They  are  pincer-like,  consisting  of  but  two  prongs. 
In  the  sea-urchins  they  are  three-pronged,  and  scattered  ir- 
regularly over  the  surface  of  the  body.  Their  use  is  not 
really  known. 

The  development  of  this  species  (and  its  ally  or  variety, 
A.  berylinus)  has  been  studied  by  A.  Agassiz,  After  pass- 


DEVELOPMENT  OF  STAR-FISHES. 


113 


ing  through  the  morula  and  gastrula  stages,  the  cephalula 
or  larval  stage  is  reached,  the  mouth,  digestive  sac  and  its 
posterior  opening  being  formed,  a  cephalic  end  being  dis- 
tinguished from  a  posterior  end.  The  larva  is  now  bilater- 
ally symmetrical.  At  this  time  two  lobes  arise  from  each 
side  of  the  mouth.  These  separate  from  their  attachment 
and  form  two  distinct  hollow  cavities,  and  by  the  time  the 
larva  attains  the  Brachiolaria  stage  the  development  of  the 


Fig.  7$.—Bipinnaria  with  the  star- 
fish budding  from  it.  e,  e',  d'.  g,  g\ 
protuberances  of  the  body  comparable 
with  the  "arms"  of  the  Brachiolaria 
figured  in  the  adjoining  engraving. 
b.  mouth;  o,  vent  of  the  larva;  A,  germ 
of  the  star-fish;  h,  ciliated  digestive 
tract;  i,  ambulacra!  rosette  (germ  of 
the  water-vessels).— After  Muller,  from 
Gegenbaur. 


ft? 


Fig.  76.— Brachiolaria 
of  Asterias  vulgaris,  en- 
larged, with  the  star-fish 
(r)  developing  at  the 
aboral  end.  e.  median 
anal  arm;  e8,  odd  termi- 
nal oral  arm;  /,  brachio- 
lar  arm;  />,  branch  of 
water-tube  (ww1)  leading 
into/"  odd  brachiolar 
arm;  fm,  surface-warts 
at  base  of  odd  brachiolar 
arm/'''.— After  A.  Agas- 
siz. 


body  of  the  star-fish  begins,  for  these  two  cavities  subse- 
quently develop  into  two  water-tubes.  On  one  of  these  cav- 
ities the  back  of  the  star-fish  is  afterward  developed,  while 
on  the  other  the  under  side  with  the  feet  or  tentacles  arise. 
The  fully-grown  larva  is  called  a  Irachiolaria,  as  it  was 
originally  described  with  this  name  under  the  impression 
that  it  was  an  adult  animal,  as  was  the  case  with  the  plu- 


114  ZOOLOGY. 

tens  of  the  sand-stars,  the  Mpinnaria  (Fig.  75)  of  certain 
star-fishes,  and  the  auricularia  of  the  Holothurians. 

Fig.  76  shows  the  star-fish  developing  on  the  aboral  end 
of  the  brachiolaria,  whose  body  it  is  now  beginning  to  ab- 
sorb. The  brachiolaria  soon  shrinks,  falls  to  the  bottom, 
and  attaches  itself  by  its  short  arms.  The  star-fish  com- 
pletely absorbs  the  soft  body  of  the  larva,  and  is  conical, 
disk-shaped,  with  a  crenulated  edge.  In  this  stage  it  re- 
mains probably  two  or  three  years  before  the  arms  lengthen 
and  the  adult  form  is  assumed. 

In  Leptycliaster  kerguelenensis  Smith,  of  the  South  Paci- 
fic, a  form  allied  to  Luidia  or  Ar chaster,  the  young  develop 
directly  in  a  sort  of  marsupium,  according  to  Wyville- 
Thompson.  Pteraster  militaris  was  found  by  Sars  to  be 
viviparous. 

In  Brisinga  the  arms  number  from  nine  to  twenty,  are 
long,  cylindrical,  and,  like  the  body,  bear  long  spines.  The 
species  are  abyssal.  B.  endecacnemos  Asbjornsen  lives  on 
the  Norwegian  coast,  at  a  depth  of  about  200  fathoms,  and 
was  dredged  in  abundance  by  the  Challenger  Expedition  in 
1350  fathoms,  at  a  station  due  south  of  St.  George's  Banks, 
associated  with  other  species  of  star-fish  (Zoroaster  and  As- 
tropecten),  and  again  in  eighty  fathoms  on  La  Have  Bank, 
off  Kova  Scotia.  A  common  form  living  in  mud  in  usually 
from  ten  to  thirty  fathoms  is  Ctenodiscus  crispatus  Eetzius, 
in  which  the  body  is  almost  pentagonal,  the  arms  being  very 
short  and  broad.  Ar chaster  is  a  genus  of  star-fishes  occurring 
at  great  depths,  A.  vexillifer  Wy  vine-Thompson  (Fig.  77), 
occurring  off  the  Shetland  Islands,  in  from  300  to  500  fath- 
oms. Luidia  is  called  the  brittle  star-fish,  as  when  brought 
up  from  the  bottom  and  taken  out  of  the  water  it  breaks  up 
into  fragments.  It  has  five  long  arms.  L.  clatlirata  is  com- 
mon on  the  sandy  shores  of  the  Oarolinas,  and  ranges  from 
New  Jersey  to  the  West  Indies.  Astropecten  articulatus 
(Say)  has  the  same  range.  Astrogonium  plirygianum  Parel 
is  a  large  pentagonal,  bright-red  star-fish,  living  in  twenty 
to  fifty  fathoms  on  rocky  bottoms  in  the  Gulf  of  Maine 
and  northward  ;  while  Pteraster  militaris  Mtiller  is  an 
arctic  species  which  ranges  south  to  Cape  Cod.  It  is  sub- 


DIFFERENT  FORMS  OF  STAR-FISHES.  115 

pentagonal,  with  five  short  arms.  The  fine  large  Solaster 
endeca  Retzius  has  eleven  smooth  arms ;  it  lives  in  deep 
water.  Crossaster  papposus  (Miiller  and  Troschel)  is  com- 
mon on  a  rocky  bottom,  in  from  twenty  to  eighty  fathoms, 
from  the  Gulf  of  Maine  northward  ;  it  is  bright  red,  and  has 
thirteen  to  fourteen  spinulated  arms.  Cribella  sanguin- 
olenta,  Liitken  is  a  common  species  on  the  coast  of  New 


Fig.  7t.—Arc7iaster  vexillifer,  under  side  ;  natural  size.— After  Wy vine-Thompson. 

England  below  low-water  mark,  and  is  in  some  respects  like 
Crossaster. 

More  closely  allied  to  Asterias  is  the  Pacific  Coast  Pycno- 
podia  helianthoides  Stimpson,  which  ranges  from  Sitka  to 
Mendocino,  Cal.  It  is  very  common  in  Puget  Sound,  under 
wharves.  Asterias  vulgaris  Stimpson  represents,  on  the 
northeastern  coast,  the  A.  rubens  of  Europe.  Asterias 
polaris  (M.  and  T.)  has  six  arms,  and  is  over  twelve  inches 


116  ZOOLOGY. 

in   diameter  ;   it   is   very  common   from  Labrador   north- 
ward. 

Fossil  star-fishes  allied  in  most  respects  to  A  sterias  occur 
in  the  Lower  Silurian  rocks,  showing  the  remarkable  persist- 
ence of  this  type  of  the  order.  Characteristic  Lower  Silu- 
rian forms  are  Palc&aster  and  Ar chaster ias.  In  the  Upper 
Silurian  appeared  Palasterina,  a  genus  allied  to  the  living 
Astrogonium,  etc. 

CLASS  II.— ASTEKOIDEA. 

EcMnoderms  with  a  star -like  or  pentagonal  body,  with  two  or  jour  rows 
of  ambulacral  feet  or  tentacles  on  the  oral  side.  Body  covered  icith  small, 
short  spines,  often  arranged  in  groups.  The  nervous  system  pentagonal, 
with  nerves  extending  into  the  arms  ;  the  water-vascular  and  hcemal  systems 
also  radiating  into  the  arms.  Most  of  the  species  bisexual ;  the  young  usually 
"passing  through  a  metamorphosis,  the  star-fish  budding  out  from  the  water- 
vascular  system  ofthepluteus,  bipinnaria  or  brachiolaria  form,  which  pre- 
viously passes  through  a  morula,  gastrula,  and  cephalula  stage. 

Ord&r  1.  Ophiuridea.-A.rms  round,  starting  suddenly  from  a  round, 
disk-like  bod}r.  Ambulacral  furrow  covered  by  a  series  of 
ventral  plates,  so  that  the  tentacles  or  ambulacral  feet  are 
thrust  out  laterally.  The  ovaries  and  stomach  not  extend- 
ing into  the  arms ;  no  anal-opening,  no  pedicellarise. 
(Ophiura,  Ophioglypha,  Ophiolepis,  Amphiura,  Ophio- 
coma,  Astrophyton). 

Order  2.  Asteridea.—Bv&y  star-like,  the  arms  being  gradual  extensions 
of  the  disk,  and  containing  the  reproductive  glands,  di- 
gestive ececa,  as  well  as  the  radial  nerves  and  radial  haemal 
and  water-vascular  canals.  A  deep  ambulacral  furrow, 
containing  two  or  four  rows  of  ambulacral  feet  or  tenta- 
cles, those  at  the  extremity  of  the  arms  without  suckers 
(Brisinga,  Ctenodiscus,  Luidia,  Astropecten,  Oreaster,  As 
trogonium,  Pteraster,  Solaster,  Crossaster,  Cribrella,  Pyc- 
nopodia,  Asterias). 

Laboratory  Work. — The  larger  star-fishes  are  easily  dissected  ;  the 
general  relations  of  the  integument  may  be  perceived  by  making 
transverse  and  longitudinal  sections,  while  the  viscera  may  be  studied 
by  splitting  the  body  and  arms  in  two  vertically.  The  smaller  Ophiu- 
rans  can  be  hardened  in  alcohol,  and  stained  sections  made  for 
studying  the  intricate  relations  of  the  water-vascular,  haemal,  and 
nervous  systems. 


HABITS  OF  SEA  URCHINS. 


117 


CLASS  III.— ECHINOIDEA  (Sea-urchins]. 
General   Characters   of  Sea-Urchins. — A   good   idea   of 
the  general   structure  of   the  members  of   this  class  may 
be  obtained   by  an    examination   of   the   common    sea-ur- 
chin, Echinus  (Fig.  78),  of  the  eastern  coast  of  the  United 


Fig.  78.— The  common  Sea-urchin,  Echinus  (Strongylocentrotus)  drobachiensis. 
d,  frame-work  of  mouth  and  teeth  seen  in  front;  <?,  the  same  seen  sideways;  a,  b,  side 
and  external  view  of  a  single  tooth  (pyramid);  all  natural  size.— After  Morse. 

States,  Northern  Europe,  and  the  Arctic  Seas.  It  is  com- 
mon among  rocks,  ranging  from  low- water  mark  to  fifty  or 
more  fathoms.  It  eats  sea- weeds,  and  is  also  a  scavenger, 
feeding  on  dead  fish,  etc.  We  have  observed  great  num- 
bers of  them  assembled  in  large  groups,  feeding  on  fish  offal, 
a  few  fathoms  below  the  sur- 
face, in  a  harbor  on  the  coast 
of  Labrador,  where  fishing- 
vessels  were  anchored. 

On  placing  an  Echinus  in 
sea-water  the  movements  of 
the  animal,  especially  its 
mode  of  drawing  itself  along 
by  its  numerous  long  tenta- 
cles or  ambulacral  feet,  and 
how  it  covers  itself  by  draw- 
ing together  bits  of  sea- 
weed and  gravel,  may  be 
observed. 

A  habit  less  easily  detected  is  that  of  some  sea-urchins 
burrowing  in  limestone  rocks  and  coral  reefs  until  the  ani- 
mal sinks  quite  far  down.  How  the  rock  becomes  thus 
worn  away,  unless  simply  by  the  rotary  movements  of  the 
body,  is  not  clearly  understood. 


Fig.  79. — Tooth -apparatus  of  the  Sea- 
urchin,  showing  the  complicated  arrange- 
ment of  the  muscles.— From  Macallister. 


118 


ZOOLOGY. 


Fig.  80.— Schematic  figures  of  a  Sea-urchin, 
the  oral  end ;  B,  from  one  side.  Ambulacra  indicated 
by  rows  of  dots,  r,  ambulacral;  ir,  interambulacral 
areas;  o,  mouth;  a,  vent.— After  Gegenbaur. 


In  order  to  examine  the  external  anatomy,  the  shell 
should  be  deprived  of  its  spines  in  part,  meanwhile  observ- 
ing the  mode  of  attachment  of  the  spines,  of  which  micro- 
scopic sections 
should  be  made. 
The  solid  mouth- 
parts,  the  oral 
membrane  sur- 
rounding the  five 
sharp  conical  teeth 
or  "pyramids," 
A,  from  and  their  mode  of 
attachment  to  the 
"  auricles  "  in  the 
shell,  should  be  thoroughly  investigated,  as  well  as  their  re- 
lations to  the  mouth-opening  and  the  digestive  canal.  The 
shell  is  a  flattened  sphere,  consisting  of  ambulacral  plates, 
perforated  for  the  exit  of  the 
feet,  and  a  broader  series  of 
five  rows  of  interambulacral 
plates  to  which  the  spines 
are  attached,  and  of  such 
form  and  arrangement  as  to 
give  the  greatest  possible 
strength  and  lightness  to  the 
shell  (Figs.  80,  81,  82).  The 
outlet  of  the  alimentary  canal 
is  situated  on  the  aboral 
(abactinal)  or  upper  end  of 
the  shell,  while  the  madre- 


poric   plate   is   Situated   upon    *a?™l iarea'  ff*  genital  plates;  iflr,  Inteigeni- 
f,  _  *    to!  plates;  m,  one  of  the  genital  plates 


Fig. 

Echinus,  with  the  upper  end  of  the  rows  of 
plates,  a,  ambulacra!  area;  i,  interambu- 
lacral  area;  g,  genital  plates;  ig,  inte 

tal  plates;  m,  one  of  the  genital  , , 

tne  top  Or  end  OI  the  Shell  formingamadreporicplate;a;,aual  opening 
/  .V  .  ,  .,  in  the  aboral  area  surrounded  by  the  genital 

(as   the  animal   moves  mouth    plates.    The  tubercles  to  which  the  spines 
u    •  T/?  are  attached  are  only  drawn  on  one  ambula- 

,  being  a  modlfica-  cral  and  one  interambulacral  area  ;  on  the 
f\f  n-nck  f\f  4-V.o,  ^  '4-  i  former  are  also  drawn  the  pores  through, 
01  One  O±  the  genital  which  the  suckers  protrode.-Aftcr  Gcgeu- 

plates(Fig.  81,  w).  There  are  baun 

five  large  plates,  one  at  each  end  of  the  interambulacral 
zones  meeting  on  the  aboral  end  of  the  body  ;  in  them  are 
the  ovarian  openings  through  which  the  eggs  escape  ;  these 


ANATOMY  OF  SEA-URCHINS. 


119 


five  plates  are  called  tlie  genital  plates,  while  in  each  of  the 
five  smaller  plates  at  the  end  of  each  ambulacral  series  is  an 

eye-speck.  The  pedicel- 
larise  are  three-pronged, 
knob-like  spines,  scat- 
tered over  the  body,  es- 
pecially near  the  moutho 
They  partly  serve  to  re- 
move the  faecal  matter, 
but  their  main  function 
is  not  known. 

Besides    the    pedicel- 

J— ^g^vMi ^i^^^^^W^  '&$2  larise,  Loven  has  discov- 
ered on  most  living 
Echini,  with  the  excep- 
tion of  Cidaris,  small 
button-like  bodies  called 
sphcBridia,  situated  on  a 

Fig.  82.—  View  of   the   calcareous   net-work  *  ,, 

from  a  plate  of  the  integument  of  a  Sea-urchin  short  Stalk,  moving  On  a 

(Cidaris)     b  section  perpendicular  to  the  hori-  T    i   1 1  i     j  j.    i,        i 

zontal nei-work  of  straight  rods.-After  Gcgen-  slightly  marked  tubercle. 

baur-  They  are  supposed  to  be 

sensorial,  probably  organs  of  taste. 
The  internal  anatomy  of  the  sea-urchin  may  be  best  studied 


Fig.  83.-Shell  of  a  Sea-urchin  (Str&ngylocentrotm  hmdus).  a,  amis;  oe,  oesophagus, 
i,  intestine;  *,  one  of  the  rods  of  the  tooth-apparatus;  m,  muscles  of  the  jaw*;  ^ ^^  ves- 
sels of  the  sucking  feet;  po,  extremity  of  the  water-vessel;  ca,  ocular  plate;  t?,  ovary. 

by  cutting  the  shell  into  two  halves,  oral  and  aboral.  Eemov- 
ingthe  aboral  end,  the  digestive  canal  may  be  seen  in  place. 


120  ZOOLOGY. 

It  consists  of  a  narrow  oesophagus  (Fig.  83,  CB),  more  or 
less  pentagonal  near  the  mouth,  dilating  into  the  stomach  ; 
and  of  a  terminal  intestine.  The  long  stomach  passes  from 
left  to  right  around  the  interior  of  the  body,  then  turns  up 
toward  the  aboral  end,  and  curves  back  in  the  opposite 
course,  again  passing  around  the  body  from  right  to  left, 
forming  two  series  of  loops  partly  enclosing  the  ovaries  ;  it 
is  held  in  place  by  abroad,  thin  membrane  or  "  mesentery." 
The  reproductive  and  other  organs  are  much  as  described 
in  the  star-fish,  there  being  five  ovaries  or  spermaries,  the 
sexes  being  distinct.  The  nervous  ring  around  the  mouth 
sends  off  five  nerves  along  the  ambulacra,  which  are  accom- 
panied by  a  water- vascular  canal  sending  branches  to  the 
tentacles,  and  a  pseudo-haemal  canal,  there  being  an  oral  and 
aboral  (anal)  haemal  ring  (their  presence  is  denied  by  Hoff- 
mann), as  well  as  an  oral  water-vascular  ring,  with  five  Polian 
vesicles  (present  only  in  the  true  Echini  and  Clypeastroids), 
a  stone-canal  and  a  fusiform  tube  or  "  heart  "*  next  to  it, 
while  the  alimentary  canal  is  accompanied  by  two  haemal 
vessels,  one  on  the  "  dorsal  "  and  the  other  on  the  free  or 
ventral  side,  communicating  with  a  lacunar  network  in  its 
walls. 

In  Echinus  it  is  difficult  to  perceive  any  bilateral  sym- 
metry, the  parts  radiating,  as  in  the  star-fish,  from  the  cen- 
tre ;  but  in  the.  Spatangus  and  allied  forms  it  is  easy  to  di- 
vide the  animal  into  a  right  and  left  side,  and  the  body  is 
more  or  less  elongated,  as  in  Pourtalesia  (Fig.  87),  the  mouth 
being  situated  at  one  end  and  the  anus  at  the  other. 

The  mode  of  development  of  the  common  sea-urchin 
(Fig.  78)  has  been  discovered  by  Mr.  A.  Agassiz.  The  earli- 
est stages  are  much  as  described  in  the  star-fish.  The  form 
of  the  pluteus  larva  is  quite  remarkable,  there  being  eight 
very  long  slender  arms  supported  by  slender  calcareous  rods 
projecting  from  the  body,  and,  during  the  movements  of 
the  animal,  opening  and  shutting  like  the  rods  of  an  um- 
brella. The  body  is  provided  with  a  sinuous  row  of  vibra- 

*  It  should  be  observed  that  the  latest  and  best  observers  are  at  vari- 
ance regarding  the  structure  and  function  of  the  so-called  Echinoderm 
"heart." 


DEVELOPMENT  OF  THE  SEA-URCHIN.  121 

tile  cilia.  When  the  larva  is  twenty-three  days  old  the  ru- 
diments of  the  five  tentacles  of  the  sea-urchin  appear.  By 
this  time  the  plutens-form  is  acquired,  and  also  at  this  pe- 
riod the  sea-urchin  growing  upon  the  deciduous  pluteus 
scaffolding  has  concealed  the  shape  of  the  digestive  cavity 
of  the  larva,  and  the  spines  are  so  large  as  to  conceal  the 
tentacles.  The  body  of  the  pluteus  is  gradually  absorbed 
by  the  growing  sea-urchin  ;  the  spines  and  suckers  of  the 
latter  increasing  in  size  and  number  with  age,  until  by  the 
time  the  larval  body  has  disappeared  the  young  Echinus  is 
more  like  the  adult  than  the  star-fish  at  the  same  period  in 


Fig.  9A.—Hemiaster  Phttippii,  with  the  young  in  two  of  the  marsupia.— From 
Wyville-Thompson's  Voyage  of  the  Challenger. 


life.  Grube  has  found  that  Anochanus  sinensis,  supposed 
to  have  come  from  the  Chinese  or  East  Indian  seas,  has 
no  metamorphosis ;  while  Hemiaster  caver nosus  of  Chili 
was  found  by  Philippi  to  carry  its  young  in  marsupia  and  to 
develop  directly. 

Several  species  of  sea-urchins  in  the  cooler  portions  of 
the  South  Atlantic,  especially  at  the  Falkland  Islands  and 
Kerguelen  Island,,  also  develop  directly  in  marsupia  or  brood- 
hollows,  without  passing  through  a  metamorphosis.  In  Hemi- 


122  ZOOLOGY. 

aster  PMlippii  Gray  (Figs.  84  and  85),  from  the  latter  island, 
certain  of  the  ambiilacral  plates  aro  greatly  expanded  and 
depressed  "  so  as  to  form  four  deep,  thin-walled  oral  cups, 
sinking  into  and  encroaching  upon  the  cavity  of  the  test, 
and  forming  very  efficient  protective  marsupia."  The 
spines  are  so  arranged  that  a  kind  of  covered  passage  leads 
from  the  ovarial  opening  into  the  marsupium,  and  along 
this  passage  the  eggs,  which  are  very  large  (a  millimetre  in 
diameter)  are  passed  and  arranged  in  rows,  each  egg  being 
kept  in  place  by  two  or  three  spines  bending  over  it.  Here 
the  eggs  develop,  and  the  embryos,  after  the  calcareous 


Fig.  85.— Marsupium  of  Hemiaster  Philippii,  containing  egg?.    Much  magnified.— 
From  Wyville-Thonipsou's  Voyage  of  the  Challenger. 

plates  once  begin  to  develop,  rapidly  assume  the  parent  form  ; 
when  they  leave  the  marsupium  they  are  about  two  and  a 
half  millimetres  long.  In  Cidaris  nutrix  Wy  ville-Thompson 
the  eggs  are  protected  in  a  sort  of  tent  by  certain  spines 
near  the  mouth.  Here  the  young  develop  without  a  meta- 
morphosis. The  allies  of  these  forms  in  the  Northern  At- 
lantic are  either  known  or  supposed  to  be  metabolous  ;  and 
Sir  Wyville-Thompson  states  that  no  free-swimming  Echi- 
noderm  larvae  (pluteus,  etc.)  were  seen  by  the  Challenger 
Expedition  in  the  Southern  Ocean. 


PRINCIPAL  FORMS  OF  SEA-URCHINS. 


123 


Taking  a  rapid  survey  of  the  principal  forms  of  sea- 
urchins,  we  may  divide  the  class  of  Echinoidea  into  two  or- 
ders :  the  Palechinida,  or  older  sea-urchins,  in  which  the 
shell  is  composed  of  more  than  twenty  rows  of  plates  ;  and 
the  Autechinida  with  twenty  rows  of  plates.* 

Order  1.  Palechinida. — Comprises  first  the  suborder  Me- 
lonitida,  in  which  there  are  more  than  ten  rows  of  ambula- 
cral  plates,  represented  by  Melonites  of  the  coal  formation, 
and  Protechiniis,  Palcechinus,  Archceocidaris,  etc.  In  the 
second  suborder  Eoeidaria,  there  are  ten  rows  of  ambulacral 
plates.  A  type  of  the  group,  Eocidaris  Kaiserlingii,  appears 
in  the  Permian  formation. 

Order  2.  Autechinida. — 
To  this  division  belong  sea- 
urchins  with  twenty  rows  of 
plates.  The  first  suborder  is 
the  Desmosticha,  comprising 
those  sea-urchins  with  band- 
like  ambulacra  extending 
from  the  mouth  to  the  oppo- 
site extremity,  and  of  more 
or  less  regular,  flattened, 
spherical  form.  Such  are 
CidariS)  Echinus,  Echinom- 
etra,  Clypeaster,  and  Echi- 
nareihnius.  The  Echinus 
esculentus  Linn.,  of  the  Mediterranean  Sea,  is  as  large  as 
an  infant's  head,  and  is  used  as  an  article  of  food. 

In  Clypeaster  the  body  is  large  and  the  shell  very  solid. 
C.  suMepressus  Agassiz  is  common  on  the  Floridan  coast. 
An  orbicular  flattened  type  are  the  sand-cakes,  of  which  the 
Echinarachnius  parma  Gray  (Fig.  86)  is  abundant  in  the 
shallower  portions  of  the  North  Atlantic,  from  low- water 
mark  to  forty  fathoms.  It  is  replaced  southward  from 
Nantucket  to  Brazil  by  Mellita  testudinata  Klein. 

The  last  suborder,  Petalosticha,  is  characterized  by  the 

*  These  are  terms  proposed  by  Haeckel,  who  regards  these  divisions 
as  subclasses,  but  we  think  they  should  more  properly  be  called  orders. 


Fig.  86. — Echinarachnius  parma,  com- 
mon Sand-cake.  Natural  size.— After  A. 
Agassiz. 


124  ZOOLOGY. 

leaf -like  ambulacra,  and  the  irregularly  heart-shaped,  often 
elongated,  form  of  the  shell,  an  anterior  and  posterior  end 
being  well  denned.  They  for  the  most  part  live  buried  in 
the  sand  or  sandy  mud,  not  moving  about  so  actively  as  the 
Desmosticha. 

Of  the  family  Spatangidce  the  singular  genus  Pourta- 
lesia  (Fig.  87,  P,  Jeffreysii  Wyville-Thompson)  deserves 
notice,  the  species  of  which  are  bottled-shaped,  with  a  thin, 
transparent  shell.  The  transition  from  such  a  form  as  this 
to  the  Holothurians  is  not  a  very  extreme  one.  This 
genus,  A.  Agassiz  states,  is  the  living  representative  of  In- 
fulaster  of  the  Cretaceous  period.  P.  miranda  A.  Agassiz 
was  dredged  in  the  Florida  Straits,  in  about  three  hundred 


Fig.  87. — Pourtalesia  Jeffreysii,  slightly  enlarged. — After  Wyville-Thompson. 

and  fifty  fathoms,  and  by  British  naturalists  in  the  'Shet- 
land Channel.  P.  Jeffreysii  was  dredged  in  six  hundred 
and  forty  fathoms,  near  the  Shetland  Islands. 

Spatangus  is  distinctly  heart-shaped,  as  is  Hemiaster. 
An  interesting  deep-sea  or  abyssal  form  not  uncommon  in 
deep  soft  mud,  at  the  depth  of  one  hundred  fathoms,  off  the 
coast  of  Maine  and  Massachusetts,  and  extending  from  Flor- 
ida around  to  Norway,  is  Scliizaster  fragilis  Agassiz. 

Echinoderms  range  to  a  great  depth  in  the  ocean,  and  are 
largely  characteristic  of  the  abyssal  fauna  of  the  globe.  In 
space  they  are  widely  distributed,  there  being  but  two 
Echinid  faunse  on  the  eastern  coast  of  the  United  States, 
one  arctic,  the  other  tropical.  While  a  large  number  of 
species  characterize  the  arctic  or  circumpolar  regions,  the 


FOSSIL  ECHINODERMS.  125 

larger  proportion  of  species  are  tropical  and  subtropical. 
Mr.  A.  Agassiz  divides  the  Echinid  fauna  of  the  world  into 
four  realms  :  the  American,  Atlantic,  Indo-Pacific,  and 
Australian. 

Though  Crinoids  were  the  predominant  type  of  Echino- 
derms  in  the  palaeozoic  rocks,  a  few  star-fish  and  Ophiurans 
appeared  in  the  Upper  Silurian  period,  and  with  them  were 
associated  one  species  of  sea-urchin,  Palcecliinus,  though 
the  genus  was  more  numerously  represented  in  the  Coal 
period.  Some  Palaeozoic  forms  resembled  the  living  gen- 
era Calveria  and  Phormosoma,  and  belong  to  the  extinct 
Carboniferous  genera  Lepidecliinus  and  Lepidesthes  ;  in  all 
these  forms,  fossil  and  recent,  the  interambulacral  plates 
overlapped  one  another  so  as  to  give  a  certain  amount  of 
flexibility  to  the  shell.  This  feature  existed  in  a  less  de- 
gree in  Arcliceocidaris.  The  characteristic  American  car- 
boniferous genera  are  Melonites,  Oligoporus,  and  Lepidechi- 
nus.  The  Permian  Eocidaris  is  nearly  allied  to  ArcJiceoci- 
daris,  so  that  it  is  a  true  palaeozoic  type  (Nicholson). 

In  the  Mesozoic  epoch  (Trias,  Lias,  and  Jura)  appeared  a 
more  modern  assemblage  of  Spatangidce,  and  genera  such  as 
Hemicidaris  and  Hypodiadema,  closely  allied  to  the  Cida- 
ridce  proper,  appeared  in  the  Trias.  The  Jurassic  beds  are 
characterized  by  genera  allied  to  Diadema,  Echinus,  Ci- 
daris,  and  a  number  of  species  of  the  families  Cassidulidce 
and  Galeritidce.  A  large  number  of  genera  survived  in  the 
Cretaceous  period,  which,  however,  is  characterized  by  the 
marked  development  of  the  Spatangidce.  In  the  Upper 
Cretaceous  the  earliest  Clypeastridce  appeared,  while  the 
Tertiary  Echinid  fauna  is  quite  similar  to  the  present  one. 
The  striking  fact  in  the  geological  history  of  the  class  is 
the  persistence  of  many  of  the  cretaceous  genera  in  the 
abyssal  or  deep-sea  fauna  of  the  present  time  (A.  Agassiz). 


126  ZOOLOGY. 

CLASS  III.—  ECHINOIDEA. 

Spherical,  heart-shaped,  or  disk-like  Echinoderms,  with  a  solid  shell  of  im- 
movable plates,  bearing  interambulacral  spines;  with  a  mouth  and  anal 
opening,  the  mouth  in  most  of  the  species  armed  with  jive  teeth ;  am- 
bulacralfeet  well  developed.  The  sexes  distinct.  Development  either  direct, 
or,  as  in  most  cases,  by  a  marked  metamorphosis  from  a  pluteus  larva. 

Order  1.  Palechinida.— Shell  composed  of  more  than  twenty  rows  of 
plates.  Suborder  1.  Melomtida  (Melonites,  Protechinus, 
Palaschinus,  Archseocidaris).  Suborder  2.  Eocidaria  (Eoci- 
daris). 

Order  2.  Autechinida. — Shell  composed  of  twenty  rows  of  plates. 
Suborder  1.  Desmosticha  (Cidaris,  Echinus,  Strongylocen- 
trotus,  Echinometra,  Clypeaster,  and  Echinarachnius). 
Suborder  2.  Petalosticha  vEchinobrissus,  Anochanus,  Pour- 
talesia,  Spatangus,  and  Schizaster). 

Laboratory  Work.  —  We  have  already  given  some  hints  as  to  the 
mode  of  dissecting  sea-urchins,  which  should  be  done  under  water  in 
deep  pans.  Great  care  must  be  taken  in  removing  the  digestive  canal, 
which  is  very  delicate  in  itself,  and  usually  filled  with  sand.  In  study- 
ing the  water-vascular  and  blood-vessels,  careful,  skilful  injections  with 
carmine  are  indispensable.  The  spines  may  be  studied  by  making  thin 
longitudinal  and  transverse  sections.  The  test,  or  shell,  should  be  de- 
nuded of  the  spines  in  order  to  study  the  relations  of  the  ambulacral, 
interambulacral,  and  genital  plates. 


CLASS  IV. — HOLOTHUKOIDEA  (Sea-cucumbers). 

General  Characters  of  Holotrmrians.— We  now  come  to 
Echinoderms  in  which  the  body  is  usually  long,  cylin- 
drical, with  a  tendency  to  become  worm-like,  and  in  cer- 
tain genera,  as  Synapta,  Chiroclota,  and  Eupyrgus,  it  is 
difficult  both  in  their  larval  stages  (Synapta)  and  in  the 
external  and  internal  anatomy  of  the  adults  to  separate 
them  from  worms  like  Sipunculus  ;  authors  have  therefore 
been  led  to  the  adoption  of  one  of  two  views  :  first,  either 
that  the  worms  and  Echinoderms  have  had  a  common  origin, 
and  the  latter,  though  truly  radiate,  have  no  near  affinities 
(though  strong  analogies)  with  the  Ccelenterates,  or  the  re- 


HABITS  OF  IIOLOTHURIANS. 


127 


semblance  between  the  two  branches  (Echinoderms  and 
worms)  is  one  simply  of  analogy,  and  involves  no  blood-rela- 
tionship. On  the  other  hand  the  radiated  arrangement  of 
parts  and  the  development  and  relations  of  the  water-vas- 
cular system  ally  them,  through  the  Ctenophores,  with  the 
Actinozoa  and  Hydroida,  and  it  seems  more  natural  to  re- 
gard the  Echinoderms  as  forming  a  branch  of  animals  in- 
termediate between  the  Hydroida  and  the  worms,  there 
being  certain  low  worms  with  a  water-vascular  system. 

But  the  student  will  be  better 
able  to  appreciate  these  general 
questions  after  a  more  or  less 
thorough  acquaintance  with  the 
forms  and  structure  of  the  pres- 
ent group.  For  this  purpose  he 
should  first  examine  living  sea- 
cucumbers,  and  then  carefully 
dissect  them.  A  detailed  study 
of  the  anatomy  of  a  Pentacta  or  a 
Holotlmria,  one  a  northern  the 
other  a  subtropical  and  tropical 
form,  and  of  a  Synapta,  found 
everywhere  along  our  coast  in  sand 
below  tide-marks,  will  give  the 
groundwork  ;  and  this  knowledge, 
autoptically  acquired,  can  then  be 
corrected  and  extended  by  reading 
^nonographs  or  compiled  state- 
ments to  be  found  in  the  more 
authoritative  general  works  on 
comparative  anatomy.  PIg>  88._Pm,ac,a  fl0ndosa.- 

Living  Holothurians  can  be  pro-  From  Teuney'<*  zoology. 
cured  with  the  dredge  or  dug  out  of  the  sand  between  tide- 
marks.     They  should  be  kept  in  aquaria,  and  their  move- 
ments watched  as  well  as  their  mode  of  locomotion,  and  the 
action  of  their  branchiae  or  external  gills  (tentacles). 

The  common  sea-cucumber,  north  of  Cape  Cod,  and  ex- 
tending through  the  Arctic  regions  around  to  Great  Britain, 
is  Pentacta  frondosa  Jaeger  (Fig.  88).  It  lives  from  ex- 


128  ZOOLOGY. 

treme  low-water  mark  to  a  depth  of  fifty  fathoms.  It  is  of 
a  tan-brown  color,  from  six  inches  to  nearly  a  foot  in 
length,  and  in  its  form  and  the  corrugations  of  its  tough, 
leathery  skin  resembles  a  cucumber  in  nearly  all  respects 
except  color.  There  are  five  series  of  ambulacral  feet,  each 
series  consisting  of  two  irregular  rows.  Around  the  mouth 
is  a  circle  of  ten  much-branched  tentacles  or  gills  (homolo- 
gous with  the  ambulacral  feet). 

On  laying  the  body  open  by  making  a  cut  extending  from 
the  mouth  to  the  vent,  the  thick  muscular  walls  of  the  body 
may  be  observed,  and  the  general  relations  of  the  viscera  to 
the  body-walls,  which  have  nothing  of  the  radiate  arrange- 
ment of  parts,  so  clearly  marked  in  the  other  Echinoderms, 
the  ambulacra,  tentacles,  and  longitudinal  muscles  alone  be- 
ing arranged  in  a  radiate  manner.  *  Unlike  other  Echino- 
derms, the  madreporic  body  is  internal,  and  there  is  a  ca- 
pacious cloaca  or  rectum,  and  a  large  vent. 

On  the  inside  of  the  body-walls  are  numerous  small  cir- 
cular (transverse)  muscles  forming  slight  ridges,  which  serve 
to  contract  the  body,  and  five  double  large  longitudinal 
muscles  (Fig.  89,  I)  lying  in  the  ambulacral  zones.  The 
mouth  is  surrounded  by  a  muscular  ring,  from  which  arise 
ten  large,  much-branched  tentacles.  The  pharynx,  or  the 
portion  corresponding  to  "  Aristotle's  lantern/'  of  the  sea- 
urchin  is  broad  and  short,  with  five  large  retractor  muscles 
(r)  originating  from  the  ambulacral  or  longitudinal  muscles 
on  the  anterior  third  of  the  body.  The  stomach  is  short, 
not  much  wider  than  the  intestines,  with  well-marked  trans- 
verse folds  within.  The  intestine  (i)  is  several  times  longer 
than  the  body,  with  longitudinal  small  folds,  and  held  in 
place  by  a  large,  broad  mesentery  which  accompanies  the  in- 
testine through  the  greater  part  of  its  length.  The  intes- 
tine terminates  suddenly,  in  a  large  cloaca  (c),  from  which 

*  In  Eupyrgus  and  Echinocucumis  it  is  difficult  to  perceive  any  radia- 
tion in  the  body  except  in  the  unbroken  circle  of  tentacles,  while  in 
Sipunculus  and  allied  worms  (Oephyrea)  the  tentacles  form  a  complete 
circle,  and  these  worms  have  a  ring-canal  and  an  imperfect  or  rudi- 
mentary system  of  vessels  thought  by  some  authors  to  correspond  to 
the  water- vascular  system  of  Echinoderms. 


ANATOMY  OF  HOLOTHURIAN8. 


129 


on  one  side  arises  the  "  respiratory  tree,"  which  has  but  one 
main  stem,  and  is  only  occasionally  held  in  place  by  mus- 
cular threads.  The  branches  are  numerous,  and  are  smaller 


Fig.  89.— Pentacta  frondosa.  t,  tentacles;  /,  longitudinal  muscles;  r,  retractor  mus- 
cles of  the  tentacular  system;  i,  intestine;  c,  cloaca;  &,  respiratory  tree;  vr,  water- 
vascular  ring  or  nng-canal,  t>,  radial  water-vascular  canal;  m.  rnadreporic  body;  pp, 
polian  vesicles;  am,  ampullae;  o,  a',  pseudo-haemal  contractile  vessels  (from  Cams); 
o,  ovary;  ov,  oviduct. — Drawn  by  J.  S.  Kiugsley  from  a  dissection  made  by  the  author. 

and  paler  than  the  ovarian  tubes.     The  water  enters  the 
cloaca  (c),  passes  into  the  respiratory  tree  (#),  oozes  out  of 


130  ZOOLOGY. 

the  ends  of  the  branches,  filling  the  body,  whence  it  is  taken 
up  by  the  madreporic  body  and  carried  into  the  water- 
vascular  system  by  the  narrow  duct  on  the  left  side  of  the 
pharynx.  Besides  being  respiratory,  this  organ  is  supposed 
to  be  depuratory  in  its  function.  In  some  Holothurians 
certain  organs  (the  Cuvierian  organs),  supposed  by  Semper 
to  be  organs  of  defence,  as  they  are  readily  thrown  out  when 
the  animal  is  disturbed,  are  attached  either  to  the  stem  of 
the  respiratory  tree  or  to  the  cloaca.  The  madreporic  body 
(m)  forms  a  rosette,  partly  surrounding  the  membrane  at- 
tached to  one  side  of  the  pyloric  end  of  the  stomach,  and 
leads  by  the  madreporic  canal,  which  is  closely  bound  down 
to  the  pharynx,  to  the  ring-canal  (vr).  Also  connected 
with  the  ring-canal  are  two  enormous  Polian  vesicles  (p,  p), 
which  are  nearly  two  thirds  as  long  as  the  body  ;  by  slitting 
up  their  base  with  scissors  they  can  be  followed  to  the  ring- 
canal.  The  latter  (vr)  is  a  capacious  canal  surrounding  the 
mouth,  and  can  be  detected  by  laying  open  the  oral- opening, 
and  then  by  cutting  across  the  longitudinal  muscles  (as  atv) 
the  radial  vessels  may  be  followed  along  the  body  under  the 
muscles.  Just  above  the  ring-canal  is  situated  the  nervous 
ring  (nr),  and  its  radial  nerves  (n)  can  be  traced  along  and 
outside  of  the  radial  water-vascular  canals.  The  ampullae 
(am)  are  red,  conical,  flask-shaped,  conspicuous  organs,  lying 
irregularly,  a  row  on  each  side  of  each  longitudinal  muscle. 
They  are  filled  with  water  from  the  small  lateral  vessels  of 
the  radial  water- vascular  canals,  The  single  ovary  is  com- 
posed of  a  large  mass  of  long  tubes,  which  are  larger  than 
and  tangled  up  with  the  branches  of  the  respiratory  tree. 
The  oviduct  is  attached  by  a  membrane  to  the  stomach,  and 
opens  between  two  of  the  tentacles  on  the  edge  of  the 
mouth. 

The  blood  or  pseudo-haemal  vessels  *  are  difficult,  without 
very  fine  dissections,  to  be  made  out.  The  system  consists 
of  a  plexus  of  vessels  lying  next  to  the  ring-canal,  from 
which  two  vessels  (a,  a')  pass  along  opposite  sides  of  the  in- 

*  These  vessels  in  Fig.  89  have  been  copied  from  Carus'  Icones  Zo- 
otomicae  ;  in  other  respects  the  drawing  represents  the  anatomy  of 
P,  frondosa. 


ANATOMY  OF  HOLOTHURIAN8.  131 

testine.     A  fluid  containing  nucleated  cells  fills  both  the 
pseudo-haemal  and  water- vascular  canals. 

HolotUuria  floridana  Pourtales  is  a  large,  dark-brown 
sea-cucumber,  with  the  feet  scattered  irregularly  over  the 
body,  and  with  smaller  tentacles  than  in  Pentacta,  which  is 
abundant  just  below  low-water  mark  on  the  Florida  reefs, 
and  grows  to  about  fifteen  inches  in  length.  The  aliment- 
ary canal  is  filled  witli  foraminifera  and  pieces  of  shells, 
corals,  etc. ;  it  is  about  three  times  the  length  of  the  body, 
and  ends  in  a  much  larger  ccecum  than  that  of  Pentacta. 
There  are  two  widely  separated  branches  of  the  "  respira- 
tory tree,"  one  being  free,  and  the  other,  tied  to  the  body- 
walls  by  thread-like  muscular  attachments,  extends  to  the 
pharynx.  The  pharynx  is  calcareous,  while  in  Pentacta  it 
is  muscular.  On  the  madreporic  body  is  a  group  of  about 
thirty  pyriform  stalked  bodies,  the  longest,  including  the 
stalk,  about  a  quarter  of  an  inch  in  length.  Succeeding 
these  bodies,  and  situated  on  the  madreporic  canal,  leading 
to  the  ring-canal,  are  a  large  number  of  Polian  vesicles,  the 
largest  one  an  inch  in  length.  The  duct  passes  spirally 
nearly  round  the  oesophagus,  and  empties  into  the  ring- 
canal  by  the  ducts  nearly  a  quarter  of  an  inch  apart.  In 
connection  with  the  tentacles  or  branchiae  are  twenty  long, 
slender  tentacular  ampullae,  not  present  in  Pentacta  and 
Tliyone.  The  ovarian  tubes  are  very  small,  some  enlarging 
and  bilobate  at  the  end. 

Closely  allied  in  external  form  to  Holotlmria  floridana, 
though  belonging  to  a  different  family  (including  Pentacta), 
is  TJiyone  Iriareus  (Lesueur),  which  lives  just  below  tidal 
marks,  from  Long  Island  Sound  to  Florida.  In  this  genus 
the  ambulacral  feet  are  not  arranged  in  rows,  but  scattered 
over  the  surface  of  the  body.  This  species  is  very  common, 
and  as  it  is  more  accessible  to  the  student  than  any  other  of 
the  sea-cucumbers,  we  give  some  points  in  its  anatomy  as 
compared  with  Pentacta,  with  which  it  is  more  closely  allied 
than  to  Holothuria.  In  a  specimen  about  eight  centi- 
metres (three  inches)  long  the  intestine  is  over  two  metres 
(about  seven  feet)  long,  the  oesophagus  opening  into  an 
oval  stomach  less  than  an  inch  in  length.  The  tentacles 


132  ZOOLOGY. 

are  capable  of  being  very  deeply  retracted,  and  as  in 
Pentacta  there  are  no  tentacular  ampullae.  The  small 
madreporic  body  is  much  as^in  Pentacta,  and  connects  with 
a  duct  (madreporic  canal)  leading  to  the  ring-canal.  There 
are  three  Polian  vesicles,  one  fusiform  and  an  inch  in 
length,  the  two  others  slenderer.  The  cloaca  is  of  mod- 
erate size,  as  in  Pentacta,  and  the  respiratory  trees  divide 
at  once  into  two  very  bushy  branches.  The  ovarian  tubes 
form  a  brush  or  round  broom-like  mass  or  tuft,  about  an 
inch  long,  the  tubes  small,  yellow,  and  of  nearly  uniform 
length,  the  oviduct  straight  and  bound  down  to  the  walls 
of  the  body. 

We  might  here  mention  the  most  aberrant  type  of  Holo- 
thurians,  the  Rhopalodina  described  by  Semper,  who  states 
that  the  body  is  flask-shaped,  with  the  mouth  and  vent  situ- 
ated near  each  other  on  the  smaller  end  of  the  body.  The 
mouth  is  surrounded  by  ten  tentacles,  and  there  are  ten 
papillae  around  the  anus.  There  is  a  spacious  cloaca  or 
respiratory  tree.  "  Ten  ambulacra  diverge  from  the  centre 
of  the  enlarged  aboral  end  of  the  body,  and  extend  like  so 
many  meridians  to  near  the  commencement  of  the  neck  of 
the  flask.  In  correspondence  with  each  ambulacrum  is  a 
longitudinal  muscular  band  ;  and  it  is  an  especial  peculiarity 
of  Rliopaloclina  that  five  of  these  are  attached  to  the  anal 
circlet,  and  five  to  the  circum-cesophageal  circlet"  (Huxley). 

The  earlier  stages  of  development  of  Holothurians,  so  far 
as  known,  is  like  that  of  star-fishes.  The  larva  when  fully 
grown  is  called  an  auricularia.  It  is  transparent,  cylindri- 
cal, annulated,  with  four  or  five  bands  of  cilia,  and  usually 
with  certain  ear- like  projections,  from  which  it  derives  the 
name  originally  given  to  this  larval  form.  Before  the  auri- 
cularia is  fully  formed  the  young  Holothurian  begins  to  bud 
out  from  near  the  side  of  the  larval  stomach,  the  calcareous, 
cross-like  spicules  appear,  and  the  tentacles  arise.  The  ear- 
like  projections  disappear,  the  auricularia  thus  becoming 
cylindrical.  It  is  soon  absorbed  by  the  growing  Holothurian, 
which  in  some  genera  is  strikingly  worm-like,  and  it  seems 
that  the  Holothurian  is  more  directly  developed  from  the 
larva  than  in  the  case  of  the  star-fish  and  sea-urchins,  the 


METAMORPHOSIS  OF  HOLOTHURIANS.  133 

metamorphosis  being  less  marked — i.e.,  growth,  is  more 
continuous,  as  in  the  Crinoids. 

In  Holothuria  tremula  and  Synaptula  vivipara  there  has 
been  observed  a  very  slight  metamorphosis,  the  young  de- 
veloping directly  in  a  marsupium,  as  in  the  star-fishes  and 
sea-urchins.  Cladodactyla  crocea  Lesson,  of  the  Falkland 
Islands,  according  to  Sir  Wyville-Thompson,  carries  its 
young  in  a  sort  of  nursery,  being  "  closely  packed  in  two  con- 
tinuous fringes  adhering  to  the  water-feet  of  the  dorsal  am- 
bulacra." He  also  found  that  in  P solus  ephippiferWyville- 
Thompson,  which  is  covered  with  calcareous  plates,  there  is 
a  dorsal  group  of  larger  tessellated  plates,  each  supported 
by  a  broad  pedicel  embedded  in  the  skin.  Under  these 
mushroom-like  plates  brood-cavities  or  cloister-like  spaces 
are  left  between  the  supporting  columns,  and  in  this  archi- 
tectural marsupium  the  embryos  directly  develop  into  sea- 
cucumbers.  It  follows  that  in  all  free-swimming  Echino- 
derm  larva?,  there  is  a  true  metamorphosis  as  distinct  as  in. 
the  butterfly,  while  in  other  forms  in  which  development  u 
direct  the  embryo  is  sedentary  and  lacks  the  cilia  and  vari- 
ous appendages  so  characteristic  of  the  ordinary  larval 
Echinoderms  ;  thus  there  are  different  stages  in  the  differ- 
ent classes  of  Echinoderms  between  direct  development  01 
continuous  growth,  and  a  complete  metamorphosis  like  that 
of  the  star-fish  or  sea-urchin,  in  which  the  pluteus  or  larva 
is  but  a  temporary  scaffolding,  as  it  were,  for  the  building 
up  of  the  body  of  the  adult. 

Turning  now  to  the  classification  of  the  Holothurians, 
and  beginning  with  the  lowest,  simplest,  most  generalized 
forms  (which  are  also  remarkably  worm-like),  and  ascend- 
ing to  higher  or  more  complicated  forms,  we  find  that  there 
are  two  orders,  those  without  feet  (Apodci)  and  those  with 
ambulacra!  feet  (Peclata).* 

*  It  is  possible  that  the  Holothurians  should  be  divided  into  two  sub- 
classes, one  Diplostomidea  Semper,  in  which  the  body  is  spherical  and 
the  mouth  and  anus  are  close  together,  with  ten  ambulacral  rows,  etc., 
and  the  normal,  cylindrical,  bipolar  Holothurians.  Semper 's  Diplostomi- 
dea is  based  on  Rhopalodina  tageniformis  Gray,  from  the  Congo  Coast, 
and  regarded  by  Semper  as  the  type  of  a  fifth  class  of  Echinoderms. 


134 


ZOOLOGY. 


Order  1.  Apoda. — The  simplest  apodous  form  is  the 
Eupyrgus  scaber  Liitken,  in  which  the  body  shows  no 
external  signs  of  longitudinal  muscles,  though  there  are 
five  small  ones,  and  is  covered  with  spine-like,  soft  papillae 
bearing  calcareous  plates.  We  have  dredged  it 
frequently  on  the  coast  of  Labrador  in  shoal- 
water.  It  has  a  circle  of  fifteen  unbranched 
tentacles,  and  is  about  one  centimetre  long. 
It  also  occurs  in  Greenland  and  Norwegian 
waters.  Myriotroclms  has  a  transparent  skin 
dotted  with  minute  white  spots,  which,  when 
magnified,  appear  to  be  wheel-like,  calcareous 
plates.  It  has  a  single  Polian  vesicle,  and  there 
is  no  respiratory  tree  nor  Cuvierian  appendages 
(Huxley).  We  have  dredged  this  beautiful 
form  (M.  Rinkii  Steenstrup)  in  sand,  in  shoal- 
water,  on  the  coast  of  Labrador.  A  very  com- 
mon Labrador  Holothurian  is  Chirodota  IcBve 
Grube  (Fig.  90).  It  lives  in  shallow,  sandy, 
retired  bays,  and  is  whitish-gray,  with  five  dis- 
tinct muscular  bands  and  scattered  white  spots, 
which  are  calcareous,  wheel-like  bodies  situated 
in  the  skin. 

[\  \  Near    Synapta,    is    Leptosynapta    Girardii 

(Verrill),  our  common  east  coast  species,  which 
''•  -       lives  in  sand  at  low  tide.    The  body  is  very 
long,  and  the  animal  when  disturbed  constricts 
its  body  and  breaks  up  into  several  pieces.     The 
skin  contains  perforated  plates  and  anchor-like 
bodies  (Fig.  91).    In  this  genus  and  those  pre- 
viously mentioned,  constituting  the  suborder 
Apneumona  and  family  Synaptidce,  the  sexes 
Fig.  90.— Chi-  are  united  in  the  same  individual,  and  there 

rodotalcwe.  Half  .  . 

natural  size.  «,  is  no  respiratory  tree,  while  the  tentacles  are 

mouth,  closed.         .        ,       *....,         -,1-1,1 

simply  digitated  or  lobulated. 

The  next  suborder,  Pneumophora,  forming  the  family 
MolpadidcB,  is  characterized  by  having  a  respiratory  tree. 
In  Caudina  the  skin  is  rough  with  calcareous  pieces,  the 


DISTRIBUTION  OF  HOLOTHURIANS. 


135 


„    91.  —  Hooks  and  plates   of 
Synapta  Girardii.—  After  Verrill. 


body  ends  in  a  long,  tail-like  prolongation ;  C.  arenata 
Stimpson  has  fifteen  four-pronged  tentacles ;  it  is  com- 
monly thrown  up  011  the  beaches 
of  Massachusetts  Bay.  A  deep- 
water  form,  a  member  of  the 
abyssal  fauna,  is  Molpadia  tur- 
gida  Verrill,  which  we  have 
dredged  in  over  one  hundred 
fathoms  in  the  Gulf  of  Maine, 
and  which  ranges  southward  to 
Florida.  It  has  a  head-end  like 
the  neck  of  a  bottle,  and  the  end  of  the  body  suddenly  con- 
tracts into  a  tail,  with  a  very  small  anus.  There  are  fifteen 
tentacles. 

Order  2.  Pedata,  or  Holothurians  with  feet.  The  mem- 
bers of  the  first  family  (DendrocJiirotm)  have  tree-like, 
branching  tentacles,  retractor  muscles,  without  Cuvierian 
organs.  It  is  represented  by  Thyone  and  Pentacta,  while 
here  belong  also  Lopliothuria  Fabricii  Diiben  and  Koren, 
P solus  pliantapus  and  P.  squamatus,  in  which  the  body  is 
armed  with  heavy  calcareous  plates,  and  the  feet  are  confined 
to  a  ventral  creeping  disk. 

In  the  highest  family,  Aspidochirota,  there  are  tentacular 
ampullae  ;  the  left  respiratory  tree  is  bound  to  the  body- 
walls,  and  there  is  a  single  ovary,  while  Cuvierian  organs 
are  present.  Holothuria  is  the  type  of  the  group.  H.  edulis 
Lesson,  of  the  Moluccas  and  Australia,  and  //.  tremula 
forms,  when  dried,  the  trepang  sold  in  Chinese  markets. 
Our  H.  floridana  has  been  dried  and  exported  to  China  as 
an  article  of  food. 

In  their  geographical  distribution  the  Apoda  are  mostly 
boreal  and  arctic.  Of  the  Pedata,  the  Dendrochirotce  are 
mostly  northern  or  arctic,  while  the  highest  group,  Aspi- 
dochirotce,  are  mainly  tropical.  Certain  genera  (Holothuria^ 
Thyone,  Psolus^Pentacta,  Chirodota,  and  Synapta)  are  almost 
cosmopolitan. 

A  few  forms  attain  a  great  depth,  and  certain  abyssal 
forms  are  often  highly  colored.  One  species,  Synapta 


136 


ZOOLOGY. 


similis,  lives  in  brackish  water,  according  to  Glaus.  Sup- 
posed plates  of  Holothurians  have  been  found  in  the 
Jurassic  rocks. 


CLASS  IV.— HOLOTHUROIDEA. 

Worm-like,  cylindrical  Echinoderms,  with  a  muscular  body-icall  ujuatty 
containing  calcareous  bodies  ;  with  a  circle  of  branched  tentacles,  a  terminal 
opening  of  the  intestine,  madreporic  plate  internal,  and  usually  a  res- 
piratory ccecal  appendage.  Unisexual  or  bisexual,  developing  by  a  metamor- 
phosis from  cylindrical,  auriculated,  free-sioimming  larva;  or  ametabolous. 

Order  1.  Apoda. — No  ambulacra!  f  eet.  Family  1.  tfynaptidce  (Eupyrgus, 
Chirodota,  Synapta).  Family  2.  MolpadidcB  (Caudina,  Mol- 
padia). 

Order  2.  Pedata. — Respiratory  tree  present,  and  the  ambulacral  feet. 
Bisexual.  Family  1.  Dendrochirotce  (Thy one,  Psolus,  Echi- 
nocucumis,  Pentacta).  Family  2.  Aspidochirotce  (Stichopus, 
Holothuria,  Aspidochir). 

TABULAR  VIEW  OF  THE  CLASSES  AND  ORDERS  OF  ECHINODEKMATA. 

Pedata. 
(Holothuria.) 


Apoda. 
(Chirodota.) 


HOLOTHUROIDEA. 


Autechinida. 
(Echinus.) 


Palechinid.a. 
(Melonites.) 

I 


ECHINOIDEA. 


Asteridea. 
(Asterias.) 


Ophiuridea. 
(Ophiura.) 


ASTEROIDEA. 


Brachiata. 

(Encrinus.) 


Cystidea. 
(Sphaeronitee.) 


Blastoidea. 
(Pentremites.) 


CRINOIDEA. 


ECHINODERMATA. 


DISSECTION  OF  HOLOTHURIAN3. 


137 


Laboratory  Work. — The  Holotlmrians  are  easily  dissected  by  cutting 
the  body  open  longitudinally,  and  pinning  the  specimen  down  in  a 
dissecting-pan,  with  wax  on  the  bottom  for  holding  the  pins.  The 
calcareous  plates  can  be  extracted  from  the  body-walls  by  being  placed 
in  a  solution  of  potash  and  mounted  in  balsam  as  microscopic  objects. 


LIBRA  R  Y 

UNIVKKS1TV   OK 

CAUFOKNfl  \. 


Encrinus  or  Stone  Lily. 


CHAPTER   V. 

BRANCH  V.— VERMES  (WORMS). 

General  Characters  of  Worms.— Having  studied  the 
one-celled  animals,  or  Protozoans,  and  the  radiated  animals, 
or  Ccelenterates  and  Echinoderms,  we  pass  to  an  assemblage 
of  forms  which  even  in  the  simplest  types  are  seen  to  have  a 
dorsal  and  ventral,  a  right  and  left  side,  and  a  head  and  tail 
end.  It  is  rare  that  the  form  of  a  worm  is  so  modified  by  its 
habits  or  surroundings  but  that  we  are  able  to  call  it  a  worm, 
though  when  we  attempt  to  draw  up  a  definition  of  the 
branch  or  sub-kingdom  Vermes,  one  which  shall  exclude  the 
worm-like  Holothurians  or  the  Mollusks,  or  certain  low  mites 
and  Crustacea,  or  even  the  Amphioxus,  we  find  it  impossible 
to  lay  down  a  set  of  characters  which  shall  accurately  and 
concisely  define  them.  This  is  due  to  the  fact  that  the  worms 
are  par  excellence  a  generalized,  synthetic  type,  from  which 
the  other  branches  of  the  animal  kingdom  above  the  Protozoa 
and  sponges  have  probably  originated.  It  will  be  well  for 
the  student  not  to  trouble  himself  at  first  about  a  definition 
of  the  branch,  but  to  study  with  care  the  leading  types,  and 
then,  in  a  review  of  the  group,  he  will  have  a  more  or  less 
definite  idea  of  the  sub-kingdom,  and  perceive  where  its  bor- 
ders, here  and  there,  merge  into  other  branches,  and  he  will 
be  then  able  to  understand  the  grounds  for  the  speculations 
regarding  the  phylogeny  or  ancestry  of  the  other  branches, 
which  have  all  an  apparent  starting-point  from  low  or  simple 
forms  resembling  such  worms  as  we  are  next  to  describe. 

As  a  provisional  definition  of  a  typical  worm,  we  may  say 
that  it  is  a  many-celled,  three-germ-layered,  bilateral  animal, 
with  a  well-marked  dorsal  and  ventral  side  and  a  head  and 
tail  end,  with  the  body  in  the  higher  forms  divided  at  reg- 


DICYEMA.  139 

ular  intervals  into  segments  (somites  or  arthromeres),  with 
usually  a  definite  relation  of  the  more  important  viscera  to 
the  body-walls — i.e.,  a  digestive  tract  extending  from  the 
head  to  the  end  of  the  body,  the  nervous  system  consisting 
of  a  brain,  or  supraoesophageal  ganglion,  and  a  single  or, 
more  commonly,  double  chain  of  ganglia,  resting  on  the 
floor  of  the  body  ;  a  dorsal  vessel  or  heart  is  usually  present 
being  situated  above  the  digestive  tract.  True  jointed 
appendages  are  never  present,  and  in  the  embryo  the 
blastoderm  is  usually  without  any  "  primitive  streak  "  (the 
Annulata  excepted).  This  definition  will  exclude  the  worm- 
like  Actinozoa  and  Holothurians. 

Before  describing  the  lowest  class  of  worms,  we  may  call 
attention  to  a  small  aberrant  group  called  Mesozoa  by  E. 
VanBeneden,  the  position 'of  which  is  doubtful,  though  the 
animals  composing  it  are  probably  aberrant  worms. 

In  1830  Krohn  observed  in  the  liquid  bathing  the  "  spongy 
bodies,"  or  venous  appendages,  of  different  species  of 
Cephalopods  certain  filiform  bodies,  covered  with  vibratile 
cilia,  and  resembling  Infusoria.  They  were  afterward  named 
Dicyema  by  Kolliker,  who  with  others  considered  them  as 
intestinal  worms.  In  1876  Professor  E.  Van  Beneden  gave 
a  full  account  of  their  structure  and  mode  of  development. 
He  states  that  these  organisms  have  no  general  body-cavity, 
but  that  the  body  consists  (1)  of  a  large  cylindrical  or  f 
form  axial  cell,  which  extends  from  the  anterior  extreifrity^j* 
of  the  body,  which  is  slightly  enlarged  into  a  head,  to  the 
posterior  end ;  (2)  of  a  single  layer  of  flat  cells  forming 
around  the  axial  cell  a  sort  of  simple  pavement  epithe- 
lium. All  these  cells  are  placed  in  juxtaposition  like 
the  constituent  elements  of  a  vegetable  tissue.  There  is 
no  trace  of  a  homogeneous  layer,  of  connective  tissue,  of 
muscular  fibre,  of  nervous  elements,  nor  of  intercellular 
substance.  There  is  only  between  the  cells  a  homoge- 
neous substance,  such  as  is  found  between  epithelial 
cells.  The  axial  cell  is  regarded  as  homologous  with  the 
endoderm  of  the  higher  animals  (Metazoa).  Van  Beneden 
designates  as  the  ectodermic  layer  the  cells  surrounding  the 
large,  single  axial  cell.  There  exists  no  trace  of  a  middle 


140 


ZOOLOGY. 


layer  of  cells,  nor  of  any  organs,  all  the  animal  and  vegeta, 
tive  functions  being  accomplished  by  the  activity  of  the 
ectodermic  cells  and  of  the  single  axial  cell.  There  is  no 
mesodermic  cell  or  cells.  On  account  of  these  characteris- 
tics. Van  Beneden 
regards  these  or- 
ganisms as  forming 
the  type  of  a  new 
branch  of  the  ani- 
mal  kingdom, 
which  he  distin- 
guishes as  Mesozoa. 
He  places  the 
branch,  or  sub- 
kingdom,  between 
the  Protozoa  and 
all  the  many-celled 
animals  (Metazoa), 
and  includes  the 
hypothetical  Gas- 
trceades  of  Haeckel 
in  the  branch. 
While  this  position 
may  prove  to  be 
the  correct  one,  we 
should  prefer,  while 
not  overlooking  the 
resemblance  of  the 
DicyemidcB  to  the 
Infusoria,  and  even 

the     GrCffarinae,    to 
. .    ,   . 

wait  for  more  light 
on  the  development 
of  the  parasitic 
Platyhelminth 
worms.  It  is  not  improbable,  on  the  one  hand,  that  the 
Dicyemidce,  retaining  their  parasitic  life,  are  retrograde 
forms,  which  have  originated  from  some  low  Cestoid  or 
Kematoid  worm,  and  bear  the  same  relation  to  them,  the 


Fig.  92.— a,  DicyemellaWi 
nucleus  of  the  axial  cell ;  b, 


flr,  g,  germigenes ;  n, 
ical  germ  of  Dicye- 
the  game  beginning 


mella,  with  its  striated  nucleus  ; 

to  undergo  self -division  ;  d,  final  stages  of  self-division 
(mornla) ;  e  and  /",  infusoriform  embryo ;  h,  germs  of 
the  vermiform  embryos  of  Dicyema  typus  ;  i,  gastrula 
of  the  same  ;  k,  I,  m,  o,  different  stages  of  vermiform 
larvae  of  Dicyema  typus,  all  highly  magnified.— After  E. 
Van  Beneden. 


FLAT- WORMS.  141 

Cestoids  especially,  which  have  no  body-cavity,  as  the  Tar- 
digrades  or  Linguatulce  do  to  the  higher  Arachnida. 

Each  species  of  Dicyema  and  Dicyemella  (Fig.  92)  com- 
prises two  sorts  of  individuals,  differing  externally,  one  (the 
Nematogene)  producing  vermiform  embryos,  the  other 
(Rhombogene)  infusoriform  (but  many-celled)  young.  The 
Nematogenes  produce  germs  which  undergo  total  segmen- 
tation, and  assume  a  gastrula  condition.  After  the  closure 
of  the  primitive  opening,  the  body  elongates,  and  the  worm- 
like  form  of  the  adult  is  finally  attained,  when  it  passes 
through  the  body- walls  of  the  parent. 

The  germs  of  the  Rhombogenes  arise  endogenously  in 
special  cells  lodged  in  the  axial  cell,  and  called  "  germi- 
genes."  The  germ-like  cells  undergo  segmentation,  and 
then  form  small  spheres,  which  become  infusoriform  em- 
bryos. The  worm-like  young  is  destined  to  be  developed 
and  live  in  the  Cephalopod  where  it  has  been  born,  while 
the  infusorian-like  young  probably  performs  the  office  of 
disseminating  the  species.  It  is  possible  that  in  those  ani- 
mals, such  as  the  Cetacea,  which  feed  on  cuttlefishes,  these 
worms  (the  Nematogenes  at  least)  may  pass  into  a  genuine 
vermian  form. 


CLASS  I. — PLATYHELMINTHES  (Flat-worms,    Tape-worms, 
Fluke-worms,  etc.) 


Order  1.    Turbellaria. — In  any  pond  of  standing  water 
one  can  find  on  the  under  side  of  sticks  or  stones,  small 
dark  flat  worms.     These  are  Planarian 
worms.      The    common     dark-brown, 
almost  black  Planaria   torva  Muller 
(Fig.  93)  is  about  six  or  eight  milli- 
metres  long,    oblong,    flat,    with   two 
black   eye-spots,  with  an   oblong  oval      Fig.  93.          Fig.  94. 
space  in  front  of  each  eye.     A  form 
allied  to  this  is  a  perfectly  white  Plana- 
rian called  Dendroccelum  lacteum  Oersted,  which  lives  under 


I 


142  ZOOLOGY. 

submerged  stones,  sticks,  and  leaves  in  ponds.  The  body 
is  partly  transparent,  with  a  dark  area  representing  the 
stomach,  from  which  branch  out  at  right  angles  a  multi- 
tude of  coecal  canals  (gastric  coeca).  It  has  two  small 
black  eye-specks.  Closely  allied  to  this  flat  worm  is  an  eye- 
less form  inhabiting  the  streams  of  the  Mammoth  and  ad- 
joining caves,  which  may  be  called  Dendroccelum  perccecum 
(Fig.  94). 

The  foregoing  forms  are  easily  obtained  by  the  student, 
who  can  study  their  habits  in  confinement.  They  all  be- 
long to  the  order  Turlellaria,  which  is  characterized  by  the 
flat,  oval  body,  covered  with  cilia.  The  ciliary  motion  can 
be  detected,  as  Moseley  has  done,  by  placing  a  little  arrow- 
root meal  or  fine  bits  of  paper  on  the  back  of  the  animal ; 
these  were  seen  to  move  in  a  forward  direction  on  the  an- 
terior part  of  the  body  of  Oeoplana  flava  Moseley,  a  Bra- 
zilian land-planarian,  and  posteriorly  they  moved  backward. 

"  In  all  regions  of  the  dorsal  surface  it  moved  outward, 
as  was  observed  by  Fritz  Miiller,  at  the  same  time  as  back- 
ward or  forward,  and  was  thus  rapidly  thrown  off  at  the 
side  of  the  body,  the  dorsal  cilia  apparently  subserving 
especially  this  function  of  the  speedy  removal  of  foreign 
substances  from  the  surface  of  the  body  "  (Moseley).  The 
structurally  the  flat  worms  may  be  understood  by  referring 
to  Fig.  95,  which  illustrates  the  anatomy  of  a  common 
European  marine  flat- worm.  The  digestive  canal  opens  by 
a  mouth  situated  usually  behind  the  middle  of  the  body, 
which  leads  into  a  chamber  containing  a  cylindrical  or 
funnel-shaped  proboscis,  capable  of  being  suddenly  thrust 
out.  The  digestive  canal  is  either  a  short  blind  sac,  or  is 
long,  forked,  and  either  simple  or  much  branched  (Fig. 
95,  e). 

These  worms  have  a  so-called  water-vascular  system,  con- 
sisting of  two  lateral  canals  and  numerous  branching  lat- 
eral stems,  with  a  common  opening  or  pore  in  the  skin  be- 
tween the  two  main  stems,  or  there  may  be  many  pores. 
The  vessels  are  ciliated  within,  and  are  supposed  to  have  a 
respiratory  or  excretory  function.  The  nervous  system  con- 
sists of  a  double  ganglion  situated  on  the  front  end  of  the 


PLANARIAN  WORMS. 


143 


body  (Fig.  95,  /),  from  which  nerves  pass  in  different 
directions,  but  a  true  nerve-cord  is  not  known  with  cer- 
tainty to  exist.*  The  eyes  are  very  simple,  indicated  by 
two  or  more,  sometimes 
thirty,  dark  pigment  spots. 
In  certain  forms,  such  as 
Macrostomum,  there  is  a  ru- 
dimentary ear  (otocyst). 

Most  of  the  Planarians, 
land  and  aquatic,  have  organs 
of  defence  in  the  form  of 
minute,  stiff  rods,  either 
coiled  up  in  an  irregularly 
spiral  manner,  or  short  and 
straight,  contained  in  oval 
cells.  These  bodies  are  shot 
out  in  great  numbers  when 
the  animals  are  irritated,  but 
are  not  retractile,  being  pro- 
jected clear  from  the  skin. 
In  being  neither  retractile 
nor  barbed,  they  differ  from 
the  lasso-cells  of  the  jelly- 
fishes.  That,  however,  they 
are  true  urticating  organs 
has  been  proved  by  Mr. 
Thwaites  (at  the  suggestion 
of  Mr.  Moseley),  who,  on 

fmipliino-     pprfain      Plpvlrmpct*    t,  male  '  genital-canal ;    k,    oviducts;    I, 
.Cnmg     Certain     UeyiOnese    Bperm-sac;   m,  opening  into  the  oviduct. 

land  -  planarians     with     his  -After  Quatretages. 

tongue,  felt  an  unpleasant  tingling  or  scalding  sensation, 

accompanied  by  a  slight  swelling. 


*  Schmarda  describes  the  nervous  system  of  Bipalium  dendrophiluz 
as  formed  of  two  pairs  of  ganglia,  from  the  hinder  of  which  arise  two  par- 
allel nerve-threads,  which  dilate  into  at  least  nine  swellings.  Moseley 
discovered  no  more  than  one  pair  of  ganglia  in  the  species  of  Bipalium 
he  examined.  Blanchard  has  demonstrated  "successive  ganglionic 
repetitions  along  the  nervous-threads  at  the  right  and  left  sides  of  the 
mid-line  of  the  body  of  a  large  Planarian  (Polycladus  Oayi  Blanch.)." — 
Clark's  "  Mind  in  Nature,"  p.  253. 


144  ZOOLOGY. 

The  Turbellaria  are  hermaphroditic,  the  ovaries  andtestes 
with  the  accessory  apparatus  (Fig.  95)  being  present  in  the 
same  individual;  but  in  many  forms  the  sexes  are  distinct. 

Little  is  known  of  the  development  of  the  flat-worms. 
In  a  common  marine  Planarian,  Stylochus  elliptica  (Girard), 
which  is  about  two  centimetres  long,  and  lives  under  stones 
between  tide-marks,  north  of  Cape  Cod,  the  eggs  are  depos- 
ited in  May  and  June,  in  a  thin,  viscid  band,  on  stones  and 
sea- weeds.  The  eggs  undergo  total  segmentation  in  four  or 
five  days  after  they  are  laid.  The  larva  is  round,  ciliated, 
with  a  caudal  flagellum.  In  eight  or  ten  days  after  the 
larva  has  hatched,  it  stops  swimming  about,  and  becomes  a 
"  mummy-  like  body,"  which  Girard  calls  a  "chrysalis." 
In  this  state  it  floats  about  in  the  water.  Its  further  his- 
tory is  unknown.  I 

In  Leptoplana  (Polycelis),  according  to  Keferstein,  the 
yolk  undergoes  total  segmentation  as  in  Styloclms ;  the 
outer  layer  of  cells  forms  a  blastoderm  which  surrounds  the 
more  slowly  growing  cells  within.  Keferstein  describes 
and  figures  the  various  stages  by  which  the  spherical  cili- 
ated embryo  attains  the  form  of  the  adult,  whose  devel- 
opment seems  to  be  less  in  the  nature  of  a  metamorphosis 
than  that  of  Stylochus. 

The  Planarians  also  in  some  species  mul- 
tiply by  fission,  and  when  cut  into  pieces, 
according  to  H.  J.  Clark,  each  piece  may 
eventually  become  a  well-formed  Planarian. 
Clark  figures  in  his  "  Mind  in  Nature"  two 
Planarians  derived  from  two  sections  of 
Dendrocwlum  lacteum,  which  became  fully 
developed  within  eleven  days  after  the  opera- 
tion. Several  Turbellarians  are  known  to 
undergo  spontaneous  fission. 

Catenula  lemnce  Duges,  by  transverse  di- 
Fig.98.-<7flfemi-  visi°n>  forms  chain-like  aggregations,  and 
goiSaSdiviskfn"  a  South  African  species,  C.  quaterna,  of 
—After  schmarda'.  Schmarda,  has  been  found  by  him  to  have  the 
same  habit.  Fig.  96  represents  two  individuals  (much 
enlarged)  in  partial  division,  and  a  chain  of  four  individ- 


LAND  PLANARIANS. 


145 


uals,  natural  size.  The  same  process  of  strobilation  has 
been  carefully  observed  by  Graff  in  Microstomum  lineare 
Oersted.  In  the  chain  of  four  individuals  (Fig.  97)  I  indi- 
cates the  division  of  the  first  order,  and  II  those  of  the 
second  order  ;  at  the  points  in  the  zooids  marked  III  there 
are  indications  of  a  future  third  subdivision,  and  at  IV  of 
a  fourth ;  so  that  potentially  the  chain  con- 
sists of  sixteen  zooids,  and  the  division  is 
first  indicated  in  the  digestive  tract  which 
forms  subdivisions  with  septa  reaching  to 
the  body-walls,  while  secondary  and  tertiary  - 
mouth -germs  appear  in  the  division-sections 
(m'9  m",  Fig.  97). 

Huxley  in  his  Manual  of  tlie  Anatomy  of 
Invertebrated  Animals  states  that  in  some 
genera  of  Turbellarian  worms  "a  difference 
is  observed  between  the  eggs  produced  in 
summer,  which  have  a  soft  vitelline  mem- 
brane, arid  those  produced  later.  These  so- 
called  winter  ova  have  hard  shells. 

The  genuine  flat- worms  are  divided  into 
two  suborders  :  Rhabdoccela  and  Dendroccela. 
In  the  former  group  there  is  an  extensible 
pharynx,  and  the  digestive  tract  is  not 
branched.  The  Ehabdocoela  are  represented 
by  Catenula,  Prostomum,  Microstomum,  etc. 

The  Dendroccela  sometimes  have  two  tenta- 
cle-like continuations  of  the  front  end  of  the 
body.  The  digestive  canal  has  one  anterior,  two 
posterior  large,  and  many  secondary  branches,  rig.  97.-strobi- 
and  a  proboscis.  Here  belong  the  Planarians  gio^hT 
of  fresh  and  salt  water,  and  the  Geoplanidce  ^ 
or  land-planarians,  represented  in  the  United 
States  by  Rhyncodesmus  sylvaticus  Leidy.  The  only  para- 
sitic species  of  the  order  known  are  Stimpson's  Cryptocce- 
lum  opacum,  which  infests  the  sand-cake  (Echinarachnius 
parma),  and  Typlilocolax  acuminata,  which  lives  on  a  Holo- 
thurian  (Chirodota)  ;  while  Semper  has  described  Anoplo- 
dium  ScJmeideri;  which  lives  in  the  intestines  of  Stichopus 


146  ZOOLOGY. 

variegatum  and  Mutter ia  lecanora,  two  East  Indian  Holo- 
thurians. 

The  Planarian  worms  merit  careful  consideration,  as  it  is 
possible  that  the  Mollusca  have  originated  from  primitive 
forms  resembling  them. 

Order  x!.  Trematodes. — Having  studied  the  Planarians, 
we  shall  be  able  to  appreciate  the  characteristics  of  the  Tre- 
matode  worms,  which  are  all  parasitic,  and  are  constructed 
on  the  dendrocoelous  planarian  type,  more  or  less  modified 
by  their  parasitic  life,  some  being  external,  but  most  of 
them  internal  parasites.  They  closely  agree  with  the  Tur- 
bellaria  in  form,  never  being  segmented.  The  mouth-open- 
ing is  usually  situated  near  the  fore-end  of  the  body  (some- 
times in  the  centre),  leading  by  a  muscular  pharynx  to  the 
digestive  canal,  which  is  forked  and  ends  in  two  coeca.  Uni- 
cellular glands  open  into  the  pharynx.  In  one  genus  (Am- 
pliilina)  there  is  no  digestive  canal. 

The  Trematodes  usually  possess  what  the  Turbellarians 
do  not  have,  a  sucking-disk  (Fig.  98,  B,  $),  situated  a  little 
behind  the  middle  of  the  body,  by  which,  they  adhere  to  the 
walls  of  the  organ  of  the  host  they  inhabit.  The  so-called 
water-vascular*  or  excretory  system  forms  a  network  of 
vessels  branching  from  two  main  lateral  tubes,  which  unite 
to  form  a  contractile  vesicle  ending  in  a  terminal  pore,  or 
the  main  branches  may  end  in  two  or  more  lateral  pores. 

The  fact  that  there  is  no  anal  opening  seems  to  confirm 
the  idea  that  the  water-vascular  system  is  excretory,  thus 
affording  the  only  outlet  for  the  waste  products  of  diges- 
tion. There  are  no  blood-vessels  or  respiratory  organs,  and 
the  surface  of  the  body  is  not  ciliated-except  in  the  embryo. 
The  nervous  system  is  usually  represented  by  a  single  gan- 
glion, like  that  of  the  Turbellarians.  Eye- spots  are  some- 
times present  in  the  young,  which,  with  other  points  in  their 
organization,  tends  to  show  that  the  Trematodes  have  origi- 
nated from  Turbellaria,  having  been  modified  by  their  para- 

*  That  the  so-called  water- vascular  system  is  mainly  at  least  excretory 
in  its  function  seems  proved  by  the  fact  that  the  fluid  is  watery  and 
contains  granular  concretions,  thus  resembling  the  urinary  excretions 
of  the  higher  animals. 


STRUCTURE  OF  FLUKE-WORMS.  147 

sitic  life,  and  with  somewhat  the  same  relations  to  Turbella- 
rians  as  Lernaean  parasites  have  to  the  normal  Copepoda,  or 
water-fleas. 

There  is  always  one  sucker  which  usually  encircles  the 
mouth,  the  other  (ventral)  sucker  varies  in  position,  and 
sometimes  there  is,  as  in  the  externally  parasitic  Polysto- 
midce  (Aspidogaster,  Polystomum,  etc.),  a  sucker  on  each 
side  of  the  mouth-opening.  In  some  forms  there  are  two 
large  chitinous  hooks  in  the  median  line  between  the  hinder 
suckers,  of  which  there  may  be  several. 

The  reproductive  glands  are  more  or  less  complicated,  and 
are  much  as  in  the  Turbellarians.  The  eggs  are  formed  (as 
in  Cestodes,  Turbellarians,  and  Eotifers)  by  two  distinct 
glands,  a  germigene  and  a  vitellogene,  the  latter  forming  the 
nutritive  mass  which  envelops  the  protoplasmic  germ  or  egg 
proper,  the  entire  mass  being  afterward  enveloped  by  the 
egg-shell.  Frequently  two  or  more  eggs  are  enclosed  in 
one  shell.  The  species  are  mostly  monoecious,  the  external 
opening  of  the  oviduct  and  the  large  intromittant  organ 
being  contiguous. 

The  development  of  the  egg  begins  by  subdivision  of  the 
nucleus  ;  the  nucleolus  then  divides,  and  subsequently  the 
protoplasmic  mass.  The  yolk,  however,  remains  entirely 
independent  of  this  division,  and  serves  as  nourishment  for 
the  other  cells  forming  the  body  of  the  embryo.  From  E. 
Van  Beneden's  observations  it  appears  that  the  eggs  of  the 
lower  flukes,  as  a  rule,  undergo  total  segmentation,  and  the 
young  of  the  Distomem  are  hatched  in  an  oval  ciliated 
"  trochosphere  "  form,  without  eye-specks,  as  in  Distoma 
and  Amphistoma  ;  or,  as  in  the  Polystomece,  there  is  no  meta- 
morphosis, but  development  is  direct,  the  embryo  passing 
directly  into  the  adult  condition. 

It  was  not  known  before  the  publication  of  Steenstrup's 
work  in  1842  that  certain  worms  called  Cercarice  were  the 
free  larval  forms  of  the  Distomes.  The  Cercaria  echinata, 
first  described  by  Siebold,  is  like  a  Distomum,  except  that 
the  body  is  prolonged  into  a  long  extensible  tail.  This  tail, 
says  Steenstrup,  is  formed  of  several  membranes  or  tubes 
placed  one  within  the  other,  of  which  the  outermost  is  a 


148 


ZOOLOGY. 


very  transparent  epidermis,  under  which  is  a  tolerably  thick 
membrane  furnished  with  transverse  muscular  fibres,  while 
between  each  pair  of  these  transverse  fibres  is  placed  a  globu- 
lar vesicle  which  appears  to  be  a  mucous  follicle  or  gland  ; 
the  innermost  tube  is  opaque  and  of  firmer  consistence  ;  it 
contains  the  longitudinal  muscular  fibres,  and  is  usually  re- 
ticulated on  the  surface.  Through  the  centre  of  these  tubes 
there  passes  a  slightly  narrower  canal,  which  becomes  very 
small  toward  the  extremity  of  the  tail.  The  existence  of 
the  same  layers  in  the  body  itself  of  the  Cercaria  can  easily 
be  demonstrated  ;  but  the  transversely  striated  layer  is  here 
not  so  much  developed. 

Steenstrup  states  that  these  Echinate  Cercariae  (Fig.  98) 


Fig.  98.— Metamorphosis  of  a  Cercaria  into  a  Distomum.  A,  parent  nurse  ;  «,  germs  ; 
a,  nurse.  S,  larva.  (7,  encysted,  pupal  Cercaria.  D,  adult  Distomum.— After 
Steenstrup. 

are  found  by  thousands,  and  frequently  by  millions,  in  the 
water  in  which  two  of  the  largest  European  fresh- water 
snails,  PlanorMs  cornea  and  Limnceus  stagnalis,  have  been 
kept.  After  swimming  about  in  the  water  some  time,  they 
fix  themselves  by  means  of  their  suckers  (B,  s)  to  the  slimy 
skin  of  the  snails,  in  such  numbers  that  the  latter  look  as  if 
covered  with  bits  of  wool. 

The  Cercaria,  by  contractions  of  its  body  and  violent  lash- 
ing of  the  tail,  forces  its  way  into  the  body  of  its  host,  loses 
its  tail,  and  then  resembles  a  mature  Distoma.  By  turning 


LIFE  HISTORY  OF  FLUKE -WORMS.  149 

about  in  its  place  and  secreting  a  slime,  a  cyst  is  gradually 
formed,  with  a  spherical  shell.  This  constitutes  the  "  pupa  " 
state  of  the  Cercaria.  Steenstrup  thinks  that  the  Cercaria 
casts  a  thin  skin.  In  this  state  the  body  can  be  seen  through 
the  shell  of  the  cyst,  as  in  Fig.  98,  (7,  where  the  circle  of 
spines  embedded  around  the  mouth  is  seen.  The  encysted 
Cercariae  remain  in  this  state  from  July  and  August  until 
the  following  spring  ;  and  during  the  winter  months,  in 
snails  kept  in  warm  rooms,  they  change  into  Distomas  (Fig. 

98,  D),   the  mature  fluke  differing,  however,  in  some  im- 
portant respects  from  the  tailless  larvae.     In  nature  they 
remain  from  two  to  nine  months  in  the  encysted  state. 

"  Now,"  asks  Steenstrup,  "  whence  come  the  Cercariae  ?" 
Bojanus  states  that  he  saw  this  species  swarming  out  from  the 
"  king's  yellow  worms,"  which  are  about  two  lines  long  and 
occur  in  great  numbers  in  the  interior  of  snails.  From  these 
are  developed  the  larval  Distomes,  and  Steenstrup  calls  them 
the  "  nurses  "  of  the  Cercariae  and  Distomes.  They  exactly 
resemble  the  "parent-nurses"  (Fig.  98,  A,  and  100),  and, 
like  them,  the  cavity  of  the  body  is  filled  with  young,  which 
develop  from  egg-like  balls  of  cells.  Steenstrup  was  forced 
to  conclude  that  these  nurses  originated  from  the  first  nurses 
(Fig.  98),  which  he  therefore  calls  "  parent-nurses."  Here 
the  direct  observations  of  Steenstrup 
on  the  Cercaria  echinata  came  to  an 
end,  but  he  believed  that  the  parent- 
nurses  came  from  eggs.  The  link  in. 
the  cycle  of  generations  he  supplied 

from   the   observations   of  Siebold,       I  /    ( 1  -   -a 

who  saw  a  Cercaria-like  young  (Fig. 

99,  B]  expelled  from  the  body  of  the 
ciliated  larva  of  Monostomum  muta- 
Ule.     Steenstrup  remarks  that  "  the 
first  form  of  this  embryo  is  not  un- 
like  that  of  the  common  ciliated  pro- 

geny  of  the  Trematoda,  as  they  have  *•  ™rse.-Afte 
been  known  to  us  in  many  species  for  a  long  time,  and  it 
might  at  first  sight  be  taken  for  one  of  the  polygastric  in- 
fusoria of  Ehrenberg,  which  also  move  by  cilia ;  whilst  in 


150 


ZOOLOGY. 


the  next  form  which  it  assumes  the  young  Monosfcomum 
bears  an  undeniable  resemblance  to  those  animals  which 
I  have  termed  *  nurses  '  and  '  parent-nurses  '  in  that  species 
of  the  Trematoda  which  is  developed  from  the  Cercaria  echi- 
nata." 

Thus  the  cycle  is  completed,  and  the  following  summary 
of  changes  undergone  by  the  Distomes  present  as  clear  a 

case  of  an  alternation  of  generations  as  seen 

in  the  jelly-fishes  : 
1-  Egg- 

2.  Morula. 

3.  Ciliated  larva. 

4.  Redia  (parent-nurse,  Proscolex)  produc- 
ing 

5.  Cercaria  (nurse,  Scolex). 

6.  Encysted  Cercaria  (Proglottis}. 

7.  Distomum  (Proglottis). 

The  Distomum  ecliinatnm  (Fig.  100),  living 
in  snails  which  are  eaten  by  ducks,  have  been 
shown  by  St.  George  to  develop  into  the  adult 
Distoma  in  the  body  of  that  bird.  It  is  gen- 
erally the  case  that  those  Distomes  which  pass 
through  an  alternation  of  generations  live  in 
the  larval  state  in  animals  which  serve  as  food 
for  higher  orders.  Thus  the  Bucephalus  of 
the  European  oyster  passes  in  the  encysted 
state  into  a  fish  which  serves  as  food  for  a 
larger  fish,  Belone  vulgaris,  in  whose  intes- 
scoiex  or  parent-  tine  the  adult  of  the  same  worm,  a  species 
mum  echinatum  of  Gasterostomum,  occurs.  The  American 


r-  oyster  is  infested  by  Bucephalus  cuculus  Ma- 
cra<iy.  It  infests  the  ovary  of  the  oyster. 
Whether  it  is  permanently  injurious  to  the  latter  is  un- 
known. 

Fasciola  liepatica  (Fig.  101),  the  liver-fluke,  sometimes 
occurring  in  man,  is  thought  by  Dr.  Willemoes-Suhm  to 
begin  its  existence  as  Cercaria  cystophora,  parasitic  on  a 
species  of  Planorbis. 

It  is  most  abundant  in  sheep  in  the  spring,  several  hundred 


HABITS  OF  FLUKE- WORMS. 


151 


occurring  in  the  liver  of  a  single  sheep.    At  this  time  it  passes 

into  the  intestine,  and  thence  is  carried  out  with  the  excre- 

ment. The  eggs  or  flukes  in  many  cases  drop 

into  pools,  ditches,  or  ponds  ;  here  the  cili- 

ated young  (like  Fig.  99)  is  liberated,  and 

soon  the  ciliae  are  absorbed,  when  it  becomes 

inert,  and  probably  soon  afterward  enters 

the  body  of  a  snail  (Planorlis,  etc.),  where 

it  transforms  into  a  large  sac,  and  devel- 

ops new  larvae  in  its  interior.     This  sac- 

like  larva  is  called  a  "nurse/''   "  sporo- 

cyst,"  or,  when  more  highly  developed,  a 

"  redia."      The  progeny  of  the  redia  is 

termed  a  "cercaria."     The  cercariae  are 

restless,  migrating  from  the  bodies  of  their 

snail-host,  and  have  been  known  in  a  few 

instances  to  penetrate  the  skin  of  human 

beings.     They  are  probably  more  usually 

,  ,        i  T        .j-,        i  -i      -i    •    -I          Fig.    101.  —  Fasciola 

swallowed  by  sheep  and  cattle  while  drink-  hepatica,  enlarged.   «., 


ing  or  grazing,  when  snail-shells  may  be 
accidentally  swallowed.  From  the  diges-  Beneden- 
tive  canal  of  sheep,  etc.,  the  cercaria  penetrates  into  the 
liver,  where  it  probably  loses  its  tail  and  becomes  encysted, 
after  many  weeks  or  even  months  becoming  a  sexually  ma- 
ture distome.  From  the  liver  it  passes  out  through  the 
liver-ducts  into  the  intestine,  and  is  finally  expelled,  thus 
completing  its  cycle  of  life  (Cobbold). 

Distomum  lanceolatum  Mehlis  differs  from  Fasciola  he- 
patica  in  the  intestine  being  simple  and  forked,  while  that 
of  the  latter  is  much  branched.  It  has  occurred  but  three 
times  in  man,  but  is  not  rare  in  the  sheep  and  ox.  It  has 
been  detected  in  Europe  in  the  pig,  deer,  rabbit,  and  hare. 
Two  immature  Distomes  have  been  found  in  the  human 
eye,  and  Cobbold  thinks  they  may  both  be  the  young  of 
D.  lanceolatum.  It  is  described  by  Diesing  under  the  name 
of  Distomum  ophthalmoMum,  is  half  a  line  in  length,  and 
occurred  between  the  lens  and  its  capsule,  appearing  as  dark 
spots  on  the  surface  of  the  lens.  Distomum  crassum  Busk 
and  D.  heterophyes  Siebold  have  each  been  only  once 


152 


ZOOLOGY. 


found  in  man,  the  former  in  a  Lascar,  the  latter  in  an 
Egyptian  boy. 

Bilharzia  hcematobia  Cobbold  is  common  in  the  portal 
system  of  blood-vessels  and  in  the  veins  of  the  mesentery, 
bladder,  etc.,  of  Egyptians,  and  has  caused  an  endemic  dis- 
ease at  the  Cape  of  Good  Hope.  In  Egypt,  out  of  three 
hundred  and  sixty- three  post-mortem  examinations,  this 
worm  occurred  one  hundred  and  seventeen  times.  It  is 
bisexual,  the  female  greatly  smaller  than  the  male,  living  in 
a  canal  or  passage  in  the  male  formed  by  the  infolding  of 
the  edges  of  the  concave  side  of  the  body,  called  a  gyncBco- 
phore.  There  are  three  other  rare  human  flukes  known  : 
Tetrastoma  renale  Delle  Chiaje,  Hexathyridium  pinguicola 
Treutler,  and  H.  venarum  Treutler,  the  latter  occurring  in 
the  veins  (Cobbold). 

The  nurse  of  Distomum  macrostomum  Rudolphi  (Fig. 
102),  described  under  the  name  of  Leucochloridium,  is 
cylindrical,  and  strongly  resembles  a  maggot ;  its  strange 
habitat  is  the  tentacles  of  a  snail  (Succinea). 

Of  the  second  suborder,  Polystomece,  the  species  have  two 
small  anterior  and  one  or  several  posterior  suckers,  and  a 

pair  of  eyes.  They  are 
mostly  external  parasites, 
like  the  leeches,  and  un- 
dergo no  metamorphosis. 
In  some  forms  the  body 
is  segmented. 

A  type  of  this  suborder 
is  Aspidogaster  conchi- 
cola  Baer,  which  inhabits 
the  pericardial  cavity  of 
fresh- water  mussels,  and 
also  is  an  ectoparasite  of  fresh-water  fishes.  Diplozoon 
consists  of  two  Trematodes  very  intimately  united  into  an 
X -formed  double  animal.  In  the  young  stages  the  two  ani- 
mals are  separate,  and  in  this  state  were  described  under  the 
name  of  Diporpa.  Diplozoon  paradoxum  Nordmann  lives  01 
the  gills  of  numerous  fresh-water  fishes.  Polystomum  has 
a  flat  body,  without  suckers  on  the  fore  end,  with  six  suck- 


pig.  102.— 1.  Lev  cockloridium  paradoxum, 
living  in  the  tentacles  of  Succinea;  2  A  full- 
grown  nurse-Leucochloridium  with  the  nurse- 
ptock  from  which  it  has  grown.  Natural  size. 
—After  Zeller. 


STRUCTURE  OF  TAPE -WORMS.  153 

ers  and  two  large  median  ventral  hooks  on  the  hinder  end. 
The  ripe  eggs  are  deposited  in  the  water  in  winter,  when 
the  ciliated  young,  with  four  eyes  and  without  suckers,  find 
their  way  into  the  gill-cavities  of  tadpoles,  whence,  during 
or  after  metamorphosis,  they  pass  into  the  urinary  bladder 
of  young  frogs  ;  P.  integerrimum  Eudolphi  lives  in  that 
of  Rana  temporaria  (Clans'  Zoologie). 

A  case  of  budding  or  parthenogenesis  is  said  to  occur  in 
the  genus  Gyrodactylus.  This  is  a  very  small  Trematode 
with  a  large  terminal  disk,  bearing  a  peripheral  set  of  pow- 
erful hooks,  with  two  long  curved  median  spines.  The 
body  of  the  hermaphrodite  worm  shelters  a  daughter,  a 
granddaughter,  and  great-granddaughter  generation.  G.  ele- 
gans  Nordmann  lives  on  the  gills  of  Cyprinoid  and  other 
fresh-water  fishes.  Dactylogyrus  lays  eggs,  not  being  par- 
thenogenetic  ;  it  has  four  head-flaps.  D.  amphibothrium 
Wagener  lives  on  the  gills  of  the  stone -perch  ;  D.  fallax 
Wagener  on  Cyprinus  rutilus. 

Order  3.  Cestodes. — The  common  tape-worm  is  the  type 
of  this  order.  Specimens  may  be  procured  from  physicians, 
and  a  careful  examination  of  cross-sections  and  ordinary 
dissections  will  convince  the  student  that  the  tape-worm  has 
no  mouth,  although  a  head  armed  with  suckers  or  hooks. 
The  body  is  divided  into  an  enormous  number  of  segments 
or  proglottids,  but  there  is  no  digestive  canal,  the  worm 
living  immersed  in  the  contents  of  the  intestines  of  its  host ; 
its  food  being  absorbed  from  the  juices  of  its  host  through 
the  walls  of  the  body. 

The  tape-worms  and  their  allies  are  not  known  with  cer- 
tainty to  have  any  trace  of  a  nervous  system.  The  water- 
vascular  system  is  well  developed  in  the  Cestodes,  where  it 
seems  to  be  excretory  in  its  functions,  as  in  the  Trematodes. 
There  are  usually  four,  sometimes  only  two,  longitudinal 
canals,  which  are  connected  in  the  head  and  in  each  segment 
with  transverse  anastomosing  branches,  while  from  these  main 
canals  a  network  of  fine  vessels  branch  out.  Granules  and 
whitish  chalky  deposits  occur  in  the  canals,  and  these  con- 
cretions, like  similar  bodies  in  the  excretory  canals  of  Tre- 
matodes, seem  to  have,  Leuckart  claims,  a  relation  like  that 


154  ZOOLOGY. 

of  the  crystals  of  oxalate  of  lime  in  the  urinary  tubes  of 
many  insects  and  the  concretions  of  phosphate  of  lime  in 
the  organ  of  Bojanus  of  Lamellibranch  mollusks.*  The 
canals  terminate  in  a  small  pulsating  vesicle  and  pore,  as  in 
the  Trematodes. 

The  Cestodes  are  hermaphroditic,  and  each  of  the  body- 
segments  except  those  nearest  the  head  contains  male  and 
female  reproductive  organs.  The  male  parts  consist,  as  in 
the  Trematodes,  of  testes,  vasa  deferentia,  and  a  muscular 
sac  with  a  cirrus  or  intromittent  organ,  which  may  penetrate 
the  vagina  of  the  same  segment.  The  female  organs  consist 
of  an  ovary  (germigene),  yolk-stock  (vitellogene),  uterus  or 
matrix,  receptaculum  seminis,  and  vagina,  the  latter  opening 
by  a  pore  situated  in  Tc&nia  (Fig.  107)  on  the  side,  or  in 
Bothrioceplialus  on  the  ventral  surface  of  the  segment. 
There  is  a  great  deal  of  variation  in  the  reproductive  organs 
of  the  tape-worms;  a  general  idea  of  the  relations  of  parts 
may  be  obtained  by  reference  to  Figs.  107  and  109.  The 
ovary  forms  the  most  important  part.  It  is  much  devel- 
oped and  very  complicated  in  structure.  As  Gegenbaur 
states  :  "  The  preservation  of  the  species  is  here  subject  to 
innumerable  difficulties,  owing  to  the  animal  living  in  dif- 
ferent hosts  at  different  stages  of  development,  and  to  the 
wanderings  which  this  mode  of  life  entails  ;  consequently  a 
large  number  of  ova  have  to  be  produced,  and  the  cer- 
tainty of  fecundation  insured."  (Elements  of  Comparative 
Anatomy,  second  edition,  English  translation.)  The 
male  organs  and  products  are  first  developed,  and  the 
receptaculum  seminis  stored  with  spermatic  cells  before  the 
eggs  fully  develop  in  the  ovary,  and  all  these  parts  develop 
earliest  in  the  terminal  segments  of  the  body  destined  to 
form  the  proglottides. 

Development  begins  very  probably,  as  in  the  Trematodes, 

*  This  is  Leuckart's  opinion.  Sommer  and  Landois  claim  that  these 
bodies  are  scattered  through  the  substance  of  the  body,  and  do  not 
occur  in  water- vessels.  Huxley  endorses  this  view.  But  if  these  bodies 
are  concretions  and  the  water-vessels  are  mainly  excretory,  as  they  cer- 
tainly appear  to  be,  we  should  judge  that  Leuckart's  view  was  the  bet- 
ter grounded. 


DEVELOPMENT  OF  TAPE-WORMS. 


155 


through  multiplication  by  division  of  the  nucleus  (germi- 
native  cell).    In  the  eggs  of  Tcenia  bacillaris  E.  Van  Beneden 


Fig.  103.—  Tcenia  solium.  Nat.  size, 
with  the  head  magnified.  Strobila  stage. 
—After  Beneden. 


Fig.  104.— Head  and  proglottisof 
T.  wtfiwm.— After  Benedeu. 


saw  the  nucleus  subdivide  ;  after  passing  through  a  morula 
condition  the  cells  are  arranged  in  two  layers,  and  the  outer 


156  ZOOLOGY. 

layer  is  thrown  off  (this  probably  corresponding  to  the  serous 
membrane  of  insects  and  Crustacea)  ;  the  central  mass 
(which  is  not  hollow  as  in  the  gustrula  of  other  worms,  a 
digestive  cavity  not  being  present  in  after  life)  forms  the 
embryo,  and  soon  three  pairs  of  hooks  arise.  Three  struc- 
tureless membranes  are  secreted  around  the  embryo,  which 
then  hatches.  The  embryo  of  Bothriocephalus  is  provided 
with  a  ciliated  membrane,  which  corresponds  to  the  first 
blastodermic  moult  of  the  embryo  Taenia,  which,  on  the 
other  hand,  is  not  ciliated. 

The  history  of  the  human  tape- worm,  Tcenia  solium  (Fig. 
103)  is  as  follows  :  the  eggs  eaten  by  the  hog  are  developed 
in  its  body  into  the  larval  tapeworm  (scolex),  called  in  this 
species  Cysticercus  celluloses  (Fig.  105  ;  Fig.  106,  head  en- 
larged). The  head  with  its  suckers  is  formed,  and  the 
body  becomes  flask-shaped ;  the  Cysticerci  then  bury  them- 
selves in  the  liver  or  the  flesh  of  pork,  and  are  transferred 
living  in  uncooked  pork  to  the  alimentary  canal  of  man. 
The  body  now  elongates  and  new  joints  arise  behind  the  head 
until  the  form  of  the  tapeworm  is  attained,  as  in  Fig.  103. 

The  hinder  joints  then  become  filled  with  eggs  and  break 
off,  becoming  independent  zooids  comparable  with  the 
"  parent-nurses  "  of  the  Cercarias,  except  that  they  are  not 
contained  in  the  body  of  the  Taenia  (as  in  the  Cercaria),  but 
are  set  free.  The  independent  joint  (Figs.  104,  107)  is 
called  a  "  proglottis. "  It  escapes  from  the  alimentary  tract 
of  its  human  host,  and  the  eggs  set  free,  in  and  about 
privies,  are  swallowed  by  that  unclean  animal,  the  pig,  and 
the  cycle  of  generations  begins  anew.  We  thus  have  the 
following  series  of  changes,  which  may  be  compared  with 
the  homologous  series  in  the  flukes  : 

1.  Egg. 

2.  Morula. 

3.  Double- walled  sac  (gastrula  ?). 

4.  Proscolex,  free  embryo  with  hooks,  surrounded  by  a 
blastodermic  skin. 

5.  Scolex  (Cysticercus,  larva).     Body  few-jointed. 

6.  Strobila  (Taenia).     Body  many-jointed. 

7.  Proglottis  (adult). 


INJURIES  CAUSED  BY  TAPE -WORMS.  157 

The  common  human  tape-worm,  Tcenia  solium  Linn., 
varies  from  ten  to  thirty  feet  in  length  ;  there  are  upward 
of  eight  hundred  joints  in  a  worm  ten  feet  long.  The  head 
ends  in  a  rostellum  or  proboscis  armed  with  a  double  crown 
of  hooks  ;  the  first  proglottis  or  sexually  mature  segment 
begins  at  the  450th.  While  in  some  persons  the  presence 
of  a  tape-worm  is  simply  an  annoyance,  in  nervous  and  irri- 
table persons  it  causes  restlessness,  undue  anxiety,  and  vari- 
ous dyspeptic  symptoms.  In  rare  cases  (over  a  hundred  are 
known)  death  has  resulted  from  the  presence  of  the  Cysticer- 


Fig.  105.— Oysti- 
cercus,     or    larval 
ape-worm. 


Fig.  106.— Head  of  Tcenia  acanthotrias  (Cyeticercue) 
enlarged,  showing  the  suckers  (S)  and  circle  of  hooks. 

cus  in  the  brain.  "  Cysticerci  may  develop  themselves  in 
almost  any  situation  in  the  human  body,  but  they  occur 
most  frequently  in  the  subcutaneous,  areolar,  and  intermus- 
cular  connective  tissue  ;  next,  most  commonly  in  the  brain 
and  eye  ;  and,  lastly,  in  the  substance  of  the  heart  and  other 
viscera  of  the  trunk  "  (Cobbold).  Among  the  preventive  rem- 
edies against  tape-worms  is  the  disuse  of  raw  or  underdone 
pork,  and  "  measly"  pork — i.e.,  the  flesh  of  swine  contain- 
ing the  little  bladder-like  vesicles.  Cysticerci,  or  larval  tape- 
worms, can  be  readily  distinguished,  but  when  thoroughly 
cooked  are  harmless,  as  the  temperature  of  boiling  water  is 


158 


ZOOLOGY. 


sufficient  to  kill  the  Cysticerci.  Butchers  especially  suffer 
from  tape-worms,  from  their  habit  of  eating  bits  of  raw 
meat,  beef  and  veal  harboring  Cysticerci,  which  transform 
into  species  of  Tcenia  nearly  as  injurious  as  Tcenia  solium. 
As  a  matter  of  course,  in  the  use  of  drugs  to  expel  a  tape- 
worm, they  should  be  pushed  so  as  to  carry  off  the  entire 
animal,  as  new  segments  grow  out  from  near  the  head  as 
rapidly  as  the  proglottides  are  detached. 

The  Cysticercus  of  another  injurious  tape-worm  lives  in 
the  muscles  and  internal  organs  of  cattle.    This  is  the  Tcenia 

mediocanellata  of  Kiichen- 
meister,  which  is  larger, 
with  a  larger  darker  head, 
d  larger  suckers,  and  with- 
out a  rostrellum  or  hooks. 
By  far  the  most  injurious 
species  is  Tcenia  echinococ- 
cus  Siebold  (Fig.  108), 
a  more  frequently  causing 
death  than  any  other  en- 
tozoon.  In  its  adult  or 
strobila  state  this  worm 
only  infests  the  dog  and 
wolf,  but  its  larva,  the 
hydatid  of  physicians,  fre- 
quently occurs  in  the  hu- 
man body.  It  is  very 
d  small,  seldom  exceeding 
six  millimetres  in  length, 
there  being  but  four 
segments,  including  the 
head,  which  has  a  pointed 

-^i^ii,,™     TrrUV,    0    /IrmKIn 
rOStellum,   With    a   QOUDle 

crown  of  large-rooted 
hooks  ;  there  are  four  suckers  present,  and  the  last  segment, 
when  sexually  mature,  is  as  long  as  the  anterior  ones  taken 
together.  The  hydatid  (proscolex)  forms  large  proliferous 
vesicles,  in  which  the  scolices  (Echmococcus  heads)  are  de- 
veloped by  budding  internally.  About  five  thousand  eggs 


rig.  io7.-progiotti8  of  T.  solium.  «,  testis  ; 

6,  sperm  duct;  c,  orifice  of  cirrus;  d,  matrix 
filled  with  eggs;  e,  vagina  ;/,  sexual  cloaca.— 


HYDATIDS.  159 

are  developed  in  a  single  segment  (proglottis).  The  six- 
hooked  embryos  develop,  are  expelled  from  the  dog,  and 
find  their  way  in  drinking-water  or  in  food  into  the  human 
intestines,  whence  they  bore  into  the  liver,  their  favorite 
habitat,  or  are  carried  along  the  blood-vessels  into  some 
other  organ,  where  they  develop  into  bladder-like  bodies 
called  acephalocysts  or  hydatids.  In  its 
earliest  stages  the  hydatid  is  spherical  and 
surrounded  by  a  capsule  of  condensed  con- 
nective tissue  of  its  host.  By  the  fourth 
week  the  young  T.  ecliinococcus  is  one  half 
a  millimetre  (one-fiftieth  inch)  in  length, 
and  it  is  probably  many  months  before  the 
Echinococci  heads  are  entirely  developed. 
"When  this  stage  is  reached  the  tape-worms 
become  sexually  mature  in  from  seven  to 
nine  weeks  after,  when  the  milk-white 
worms  may  usually  be  found  embedded  in 
the  mucus  of  the  duodenum  and  upper 
part  of  the  small  intestines,  with  their 
heads  attached  to  the  villous  surface  of 
the  intestine.  The  hydatids  or  cysts  in 
which  the  Echinococci  develop  are  of 
three  kinds — viz.,  exogenous,  endogenous, 
and  multilocular,  and  lie  embedded  in  the 
parenchym  of  the  liver,  etc.,  and  are  filled 
with  a  clear  amber-colored  fluid.  The 
Echinococcus  heads,  first  on  the  inner  sur- 
face of  the  cyst  and  in  the  interior  of  the 
Echinococcus-head  (brood-capsule),  devel- 
ops a  second  brood  of  scolices,  contained 

,  T-I-       11  j__t«  Fig.     108.  —  Tcenia 

in  a  secondary  cyst,  finally,  a  tertiary  ecMnococcus .  —  After 
cyst,  containing  tertiary  or  granddaughter  B 
scolices,  arises.  Sometimes  the  secondary  hydatids  will  de- 
velop scolices  and  granddaughter  vesicles  before  the  original 
maternal  hydatid  has  acquired  Eohinococcus  heads  (Cob- 
bold). 

The  largest  human  tape-worm  is  Bothrioceplialus  latus 
Bremser  (Fig.  109). 


160 


ZOOLOGY. 


This  worm  is  extremely  rare  in  America,  but  is  common  in 
Western  Switzerland  and  Central  Europe,  and  in  the  north- 
western and  northern  provinces  of  Kussia,  Sweden,  and 
Poland.  It  is  sometimes  twenty-five  feet  long,  and  nearly 
an  inch  broad,  with  4000  joints.  The  club-shaped  head  is 
unarmed,  and  the  first  sexually  mature  segment  is  about 


Fig.  109.— Male  reproductive  organs,  with  parts  of  the  female  of  Bothriocephalus 
latus.  t,  testicular  follicles,  only  a  part  are  represented  ;  ve,  their  excretory  ducts  ; 
vd,  vas  deferens  ;  c,  cirrus  ;  cb,  sac  containing  the  cirrus  ;  «,  uterus  containing  eggs  ; 
o»,  ovary  ;  gl,  shell-gland  ;  e,  water-vascular  trunks  ;  v,  vaginal  canal.— After  Landois 
and  Sommer  ;  from  Gegenbaur. 

the  600th  from  the  head.  Leuckart  has  suggested  that 
the  young  of  this  tape-worm  originate  in  salmon  and 
trout. 

The  sheep-hydatid  is  the  larva  of  Tcenia  ccenurus  (Figs. 
110  and  111),  the  adult  infesting  the  dog.  The  presence  of 
one  or  several  of  the  hydatids  in  the  brain  of  the  sheep  pro- 
duces the  "  staggers  "  or  vertigo.  The  vesicle  varies  in  size 
from  a  pea  to  a  pigeon's  egg.  It  is  bladder-like,  filled  with 
a  clear  pale  yellow  albuminous  secretion,  with  a  great  num- 
ber of  retractile  papillae  (Z),  g),  which  are  the  tape-worm  heads 
connected  by  narrow  stalks  to  the  common  vesicles  support- 


•' 


HTDATIDS  OF  THE  SHEEP.    *> 


. 

ing  the  colony.     This  hydatid  also  infests  cattle,  the  horse, 
goat,  various  species  of  antelope  and  deer,  the  dromedary, 
and,  it  is  said,  the  rabbit.    "  In  the  sheep  the  disease  is  re'c*-/ 
ognized  at  first  by  a  heavy,  stupid,  wandering  gait,  which     / 


Fig.  110.— A,  train  of  a  sheep  which  three  weeks  previous  had  swallowed  some  eggs 
of  T .  ccenurus,  and  which  was  killed  after  having  shown  all  the  symptoms  of  "  stag- 
gers.'1 B  b,  isolated  gallery  formed  by  the  worm  at  the  surface  of  the  brain,  the  sec- 
lex  being  found  at  the  end  of  the  gallery, 
the  scolex.  B  d,  vesicle  in  which  the  sc 


isolated  gallery  formed  by  ._ 

tilery.    Be,  vesicle  (proscolex)  before  the  birth  of 

the  scolices  will  appear.     C,  vesicles  which  have 

produced  some  pcolices.  Z>,  the  hydatid  vesicle  containing  gg,  the  secondary  vesicles. 
E,  scolex  of  T.  cwnurus,  corresponding  to  a  secondary  vesicle  D  g,  and  very  much 
magnified  and  invaginated.  a,  point  at  which  the  head  of  the  worm  will  issue  out ; 
b.  point  of  junction  with  the  hydatid  vesicle  ;  c,  hooks  ;  (t,  the  suckers  ;  e,  the  neck  ; 
/,  the  wall  of  the  hydatid  cyst.— After  Beneden. 


is  frequently  succeeded  by  irregular,  tortuous,  whirling 
movements  of  the  body,  accompanied  with  convulsions  (Cob- 
bold). 

The   simplest  form   in   the   order  is  Caryophyllaus,  in 
which  the  body  is  not  jointed  in  the  adult,  though  it  is  so 


162  ZOOLOGY. 

in  the  young,  and  there  are  no  suckers  or  hooks  ;  while 
there  is  but  a  single  set  of  male  and  female  reproductive 
organs  situated  in  the  posterior  end  of  the  body,  which  can 

be  detached  from  the  ante- 
rior part  of  the  body,  form- 
ing a  proglottis.  In  fact, 
this  form  is  a  connecting 
link  between  the  Trematoda 

Fig.m.-HealofT'.c.^Beenfrom  «ld  Ctefcxfe..  CaryOphyllCBUS 
above,  with  circle  of  hooks  ;  a— e,  hooks  ;  mutaulllS  Rudolphl  llVCS  in 
all  much  enlarged.— After  Siebold.  ....  \  ~.  • -, 

the  intestines  of  Cyprmoid 
fishes  ;  the  young  in  a  worm,  Tubifex  rivulorum. 

Tetraryhnclius  is  provided  with  four  very  long  slender 
extensile  spiny  cephalic  processes  or  beaks.  The  young  live 
encysted  in  bony  fishes,  the  adults  occurring  in  the  intestines 
of  sharks  and  rays. 

In  Ligula  the  body  is  ribbon -shaped,  not  jointed,  with  a 
series  of  sexual  organs,  and  there  are  no  suckers,  and  some- 
times no  hooks.  L.  simplicissima  Eud.  lives  in  fishes  and 
amphibians,  and  attain  maturity  in  the  intestines  of  water- 
birds,  which  feed  on  the  former  animals.  This  genus  con- 
nects the  simpler  tape-worms  with  Bothriocephalus  and 
Tcenia. 


CLASS  L—  PLATYHELMINTHES. 

More  or  less  flattened  worms,  with  the  body  usually  unsegmented ;  the 
head  in  the  Cestodes  often  armed  with  hooks  or  suckers.  Simple  or  branched 
(Turbellaria)  or  forked  (Trematoda)  digestive  tract,  but  no  general  body- 
cavity.  (The  digestive  cavity  is  entirely  wanting  in  the  Cestodes.}  Nervous 
system  represented  by  a  cephalic  ganglion,  which  in  the  Cestodes  is  absent.  A 
system  of  vessels  corresponding  to  tJie  water-vascular  system  of  Echinoderms, 
but  supposed  to  be  mainly  excretory  in  function.  Monoecious,  rarely  bi- 
sexual. Ovaries  differentiated  into  a  germigene  and  vitellogene  ;  often  par- 
thenogenetic,  accompanied  by  strobilation  in  the  tape-worms.  When  alter- 
nation of  generations  occurs  by  budding,  the  sexual  animals  are  united  with 
their  nurse  or  a  sexual  form  into  a  polymorphic  colony. 

Order  1.  Turbellaria. — Flattened  ovate  worms,  with  a  nervous  gan- 
glion in  the  head  ;  usually  eye-specks  ;  body  externally  cili- 
ated, with  a  much -branched  digestive  canal.  Nettling 
organs  often  present.  Unisexual,  rarely  bisexual ;  strobi- 


THREAD-WORMS. 


163 


lation  very  rare  ;  a  metamorphosis  in  the  Dendroccda,  the 
larva  being  a  trochosphere.  Suborder  1.  Rhabdoccda  (Mo- 
nocelis,  Catenula,  Mesostomum).  Suborder  2.  Dendroccela 
(Planaria,  Dendrocceluin,  Geoplana,  and  Bipalium). 

Order  2.  Trematoda. — Usually  flat,  oval,  rarely  cylindrical,  not  seg- 
mented, parasitic  worms,  with  a  mouth,  forked  intestine, 
no  anus  ;  a  large  sucker  near  the  middle  of  the  body,  or 
several  smaller  ones  ;  either  with  a  metamorphosis  (Dis- 
tomese),  the  larva  living  in  mollusks,  etc.,  the  adult  in  ver- 
tebrates ;  or  with  direct  development  (Polystomece).  Sub- 
order 1.  DistomecB  (Monostomum,  Amphilina,  Distomum, 
Amphistomum).  Suborder  2.  PolystomecB  (Aspidogaster, 
Diplozoon,  Polystomum,  Gyrodactylus). 

Order  3.  Cestodes. — Parasitic,  usually  ribbon-like  worms,  without  any 
mouth,  digestive  canal,  or  nervous  system  ;  with  an  (ex- 
cretory) water-vascular  system  ;  hermaphrodite,  the  joints 
(proglottis)  numerous  and  containing  male  and  female  re- 
productive organs  ;  the  eggs  minute  and  very  numerous. 
The  mature  worm  is  many-jointed,  the  joints  budding  out 
from  near  the  head  ;  in  this  form  it  is  called  a  strobila  ; 
the  terminal  joints  fall  off,  becoming  independent  (proglottis). 
The  eggs  after  fertilization  pass  through  a  morula  and 
gastrula  stage,  a  circle  of  hooks  and  suckers  developing  on 
the  head  (Caryophyllaeus,  Tetrarhynchus,  Ligula,  Both- 
riocephalus,  Taeina). 

Laboratory  Work.— The  flat  worms  have  been  most  successfully 
studied  by  fine  injections,  especially  by  slicing  hardened  sections, 
which  should  be  stained  with  carmine,  and  mounted  for  the  micro- 
scope. 


CLASS  II.—  NEMATELMINTHES  (Round,  Thread-worms). 

General  Characters  of  Thread-worms.— These  worms  are 
either  free  or  parasitic  ;  examples  of  the  former  exist  in 
abundance  under  stones,  etc.,  between  tide-marks,  lying 
in  coils ;  small,  almost  minute  species  occurring  in  fresh 
water  and  in  damp  earth,  while  the  parasitic  species,  which 
are  the  most  numerous,  live  free  in  the  alimentary  canal  or 
imbedded  in  the  flesh  of  their  hosts,  especially  fishes  and 
mammals.  The  species  are  remarkably  persistent  in  form, 


164  ZOOLOGY. 

the  specific  and  generic  differences  being  very  slight.  They 
have  a  mouth  and  digestive  canal  (except  in  EcliinorhyncJius), 
the  integument  being  hard,  chitinous,  and  not  segmented 
(except  in  Desmoscolex,  which  approaches  in  this  respect  the 
annelids),  and  usually  smooth,  except  in  Ecliinoderes,  which 
is  variously  armed  with  hair-like  spines.  Each  end  of  the 
body  is  much  alike,  the  mouth  situated  at  the  anterior  end, 
and  the  anal  opening  at  or  near  the  conical  tip  of  the  body. 
There  are  two  long  vessels  which  extend  from  a  single  com- 
mon pore  situated  on  the  median  line  of  the  under  side  of  the 
body,  a  short  distance  from  the  head  ;  these  are  supposed  to 
be  excretory  vessels.  In  Ascaris  and  Oxyuris  a  nervous  ring 
surrounds  the  oesophagus,  from  which  two  nervous  threads, 
one  dorsal  the  other  ventral,  pass  to  the  end  of  the  body,  and 
there  are  six  other  smaller  longitudinal  nerves.  The  gangli- 
onic  cells  lie  near  the  nervous  ring,  forming  a  suboesopha- 
geal,  supracesophageal  and  lateral  ganglion,  and  there  is  also 
a  caudal  ganglion.  In  some  free-living  Nematodes  there  are 
eye-specks. 

The  Nematodes  are  usually  bisexual ;  Pelodytes  is  her- 
maphroditic, while  the  same  individual  of  Ascaris  nigrovenosa 
at  first  produces  sperm-cells  and  afterwards  eggs.  The  males 
differ  from  the  females  in  their  smaller  size  and  the  usually 
curved  end  of  the  body.  "While  most  of  these  worms  lay 
eggs,  some,  as  in  Trichina  spiralis,  bring  forth  their  young 
alive. 

The  mode  of  development  of  these  true  Nematode  worms 
(Echinorhynclms  excepfced)  so  far  as  known  is  quite  uniform, 
growth  being  direct,  without  any  metamorphosis.  The 
germ  is  formed  in  three  ways  :  (1)  usually  the  egg  under- 
goes total  segmentation ;  (2)  others,  as  in  Ascaris  dmtata 
and  Oxyuris  ambigua,  do  not  show  any  apparent  trace  of  seg- 
mentation, while  (3)  in  Cucullanus  elegans  there  is  no  yolk, 
the  nucleus  absorbing  all  the  vitelline  matter,  which  is  lim- 
pid and  transparent.  The  germ  consists  of  a  single  series  or 
circle  of  cells  bent  on  itself,  somewhat  as  in  Fig.  120,  which 
represents  a  little  more  advanced  stage  in  Sagitta,  and  there 
are  a  few  cells  representing  the  endoderm.  The  embryo 
rapidly  assumes  the  adult  form  before  hatching. 


THE  ECHINORYNCHUS.  165 

Order  1.  Acantliocepliall. — These  are  aberrant  Nematode 
worms  (sometimes  referred  to  a  separate  class),  without  any 
mouth  or  digestive  tract,  but  with  an  extensible  spiny  beak, 
living  by  imbibition  of  the  fluids  of  the  alimentary  canal  of 
their  host. 

The  thick  subcuticula  is  penetrated  by  a  network  of  ves- 
sels, whose  trunks  form  two  oval  bodies  of  unknown  use 
called  lemnisci,  which  hang  down  free  in  the  body-cavity. 
The  sexes  of  Ecliinorhynchus  are  distinct.  The  eggs  are 
usually  spindle-shaped.  The  embryo  develops  in  the  body 
of  the  parent  worm,  and  is  surrounded  by  several  membranes, 
with  a  circle  of  hooks  arranged  bilaterally  around  the  mouth. 
The  embryo  contains  an  oval  mass  of  nuclei,  being  the  ru- 


Pig.  llZ.—Echinoi'ynchus,  head  retracted  and  in  the  second  figure  extruded  ;  mag 
nified.    a,  oval  pore  ;  b  b,  protractile  muscles ;  c  c,  lemnisci.— After  Owen. 

diments  of  an  intestinal  canal.  Finally  it  passes  into 
some  crustacean  or  insect,  in  whose  body  it  becomes  so  far 
developed,  that  when  its  host  is  swallowed  by  some  vertebrate, 
such  as  a  fish,  the  embryo  is  liberated  in  the  intestines  of  the 
second  (vertebrate)  host  and  soon  attains  sexual  maturity. 
Nearly  a  hundred  species  are  known. 

Ecliinorliyncliusyiyas,  the  female  of  which  is  50f  centime- 
tres (20  inches)  in  length,  lives  in  the  small  intestine  of  the 
pig.  Its  eggs  pass  out,  becoming  scattered  on  the  ground, 
where  they  are  eaten  by  the  white  grub  or  larva  of  the  Euro- 
pean cockchafer.  The  egg-membranes  burst  in  the  stomach 
of  the  grub,  and  the  embryos  thus  liberated  penetrate,  by 


1C6  ZOOLOGY. 

means  of  their  spines,  through  the  intestine  into  the  body- 
cavity  of  the  larva,  where  they  become  encysted,,  and  the  latter 
being  in  the  beetle  state  devoured  by  the  pig,  finish  their  de- 
velopment in  the  intestines  of  the  latter  animal.  (Schneider. ) 
The  embryos  of  this  species  also  occur  in  the  land-snails,  and 
those  of  E.  claviceps  have  been  found  in  fresh-water  snails 
(Limncea).  Young  Echinorliynchi  occurring  in  the  copepod 
crustacean,  Cyclops,  become  mature  in  a  fish  ( Gadus  lota). 
Leuckart  has  also  found  that  a  sexless  form  living  in  a  fresh- 
water crustacean,  Gammarus  pidex,  becomes  developed  to 
sexual  maturity  in  the  perch,  which  feeds  on  the  crustacean. 
They  attain  the  mature  form,  though  the  eggs  are  not  ripe, 
in  eight  or  ten  weeks  after  the  eggs  from  which  they  hatch  are 
laid,  and  look  like  round  or  oval  yellowish  balls  from  one  to 
one  and  a  half  millimetres  in  length.  The  males  mature  in 
about  a  week  after  the  females. 

The  primary  host  of  Ecliinorliynclms  angustatus  is  the 
fresh-water  sow-bug  (Asellus).  After  the  eggs  find  their 
way  into  the  intestines  of  the  Asellus,  the  embryos,  on  hatch- 
ing, pass  through  the  walls  of  the  hinder  part  of  the  chyle- 
stomach  of  the  Asellus  into  the  body-cavity,  by  means  of 
the  embryonal,  deciduous  neck  apparatus ;  and,  as  in  E. 
proteus,  the  embryos  lie  between  the  chitinous  walls  of  the 
intestine  and  the  muscular  layer.  The  embryos  are  round- 
ed, more  or  less  spindle-shaped,  with  a  so-called  rudimentary 
digestive  cavity  indicated  by  a  central  circle  of  cells,  the 
cells  of  the  body- walls  being  situated  in  a  parenchymatous  or 
protoplasmic  mass  (plasmodium),  being  thus  comparable  to 
the  blastoderm  of  some  insects.  The  embryo  is  0.09-0.1 
millimetres  long.  The  form  of  the  body  now  becomes  irreg- 
ularly oval  or  cylindrical,  being  quite  protean  in  shape,  with 
often  a  projection  on  one  side  of  the  end  of  the  body.  The 
Echinorhynchus  form  then  begins  to  appear,  the  metamor- 
phosis being  very  marked.  The  first  step  is  the  moulting  of 
the  embryo  or  larva,  which  loses  its  spines.  After  a  few 
weeks  the  Echinorhynchus  form  is  attained,  the  body  being 
elongated,  and  with  the  reproductive  organs  developed,  but 
with  no  hook-apparatus.  It  is  now  7  to  8  millimetres  in 
length,  and  almost  as  long  as  its  host,  the  Asellus  ;  the  males 


THREAD-WORMS. 


107 


being  smaller  and  shorter  than  the  females.     With  the  ex- 
ception of  the  skin  and  lemnisci,  all  the  parts  of  the  adult 
worm,  the  nervous  and  reproductive  systems  as  well  as  the 
beak,  originate  in  the  primitive 
rudimentary     digestive     cavity, 
appearing  as  rounded  masses  of 
cells  of  like  size,  but  differing  in 
structure    histologically.      With 
the   growth  of   the  beak  begins 
the  development   of   the   repro- 
ductive apparatus,  and  the  hooks 
are  simply  modified  cells,  with 
the  outer  surface  chitinizecl. 

Order%.  Nematodes. — The  first 
suborder  of  this  group,  compos- 
ing the  true  round  worms,  is  re- 
presented by  Ascaris,  Oxyuris, 
Trichina,  etc.  The  human 
round  worm,  Ascaris  lumbri- 
coides  Linn.  (Fig.  113),  is  re- 
markable for  its  large  size,  and 
may  be  recognized  by  its  milk- 
white  color,  as  well  as  by  the 
three  papillae  around  the  mouth. 
It  inhabits  the  intestines,  some- 
times the  stomach  and  oesopha- 
gus, and  has  been  known  to  per- 
forate the  walls  of  tho  intestine. 
The  species  of  Ascaris  are  very 
numerous,  infesting  mammals, 
and  especially  fish,  often  occur- 
ring encysted  in  the  flesh  of  tho 
cod  and  other  edible  salt  and  Fig.  us.— Ascaris lumMcoides.  <\ 

n   i       11  female,  natural  -ize.    6,  heart-end  en- 

Water     nsn,     but    are     as    a     larged;  c,  the  same,  front  view  show- 


rule  harmless.  Ascaris  mystax 
lives  in  the  intestines  of  the 
cat. 

The  common  pin-worm  lives  in  the  rectum  of  children. 
It  is  the  Oxyuris  vermicularis  Linn.  (Figs.  114,  115).     The 


168 


ZOOLOGY. 


female  is  white  and  from  eight  to  ten  millimetres  in  length; 
the  male  is  only  two  or  three  millimetres  long. 

The  largest  known  round  worm  is  the  palisade  worm,  or 
Eustrongylus  gigas  Rudolphi,   the  female  of  which  is  a 


Kg.  114.-  Ox- 

yuris  vermicula- 
•ris.  a,  male,  nat- 
ural size ;  b,  the 
same  enlarged.  — 
After  Beneden. 


Fit?.  115.—  Oxyitri* 
yrrmiculari*.  a,  fe- 
male, Natural  size ;  b, 
the  same  enlarged. — 
After  Beneden. 


Fig.  1 1 6. — Trichocephalus  dis- 
par.  a,  male,  natural  size  ;  6, 
enlarged  ;  c,  female,  natural 
size.— After  Beneden. 


metre  (about  39  inches)  in  length,  and  the  size  of  a  quill ; 
the  male  is  one  third  as  long.  It  is  rare  in  man,  and  occurs 
especially  in  the  intestines,  and  sometimes  the  kidneys  of 
such  mammals  as  live  on  fish.  The  mouth  is  surrounded 


THE  TRICHINA. 


169 


by  six  tubercles.  Eustrongylus  papillosus  Diesing,  accord- 
ing to  Wyman,  lives  coiled  up  in  the  bruin  of  the  anhinga, 
or  snake-bird  of  Florida.  E.  buteonis  Packard  was  found 
living  under  the  eyes  of  Buteo  Swainsoni,  and  E.  cliordeilis 
Packard  in  the  brain  of  the  night-hawk.  Doclimiiis  duoden- 
alis  Dubini  lives  in  the  small  intestine  of  man. 

TricliQceplialus  dispar  Biidolphi  (Fig.  110)  lives  in  the 
coecum  of  man,  with  the  smaller  anterior  part  of  the  body 
buried  in  the  mucous  membrane. 

The  most  formidable  round  worm  is  the  Tr4ckina  spiraUs 
Owen  (Fig.  117).  The  body  is  regularly 
cylindrical,  tapering  gradually  from  the 
posterior  end  to  the  head.  The  end  of  the 
body  of  the  male  is  without  a  spiculum,  but 
with  two  conical  terminal  tubercles.  It  is 
1.5  millimetres  long.  The  female  is  3  mil- 
limetres in  length. 

Viviparous  females  begin  about  eight  days 
after  entering  the  intestine  of  their  host  to 
give  birth  to  the  larva?,  which  bore  through 
the  walls  of  the  intestines  of  their  host, 
passing  into  the  body-cavity,  and  partly  in- 
to the  connective  tissue,  and  also,  by  means 
of  the  circulation,  into  the  muscles.  In 
about  fourteen  days  the  worm  coils  up 
spirally  in  a  cvst  (Fig.  117),  which  evcntu- 

11     i  iv  i       i  •   •  i        ITTI 

ally  becomes  calcareous  and  whitish.  \V  hen 
the  flesh  of  the  pig,  infested  by  the  encysted 
larvae,  is  eaten  by  man,  the  young  worms  artl 
are  set  free  in  the  stomach  of  their  new  host,  and  in  three 
or  four  days  become  sexually  mature.  The  female  Trichina 
is  capable  of  producing  a  thousand  young.  The  original 
host  of  the  Trichina  is  the  rat ;  dead  rats  are  often  de- 
voured by  pigs,  and  the  use  of  raw  or  partially  cooked  pork 
as  food  is  the  means  of  infection  in  man. 

Another  worm,  occasionally  parasitic  in  sailors  and  resi- 
dents of  the  East  Indies,  is  the  Filaria  medincnsis  Gmclin, 
or  Guinea-worm.  It  is  remarkably  long  and  slender,  some- 
times over  two  feet  in  length.  The  female  is  viviparous, 


170 


ZOOLOGY. 


while  the  male  is  unknown.  The  worm  lives  in  the  con- 
nective tissue  under  the  skin,  especially  of  the  extremities. 
As  the  body  of  the  female  is  full  of  young,  the  worm  has  to 
be  carefully  and  slowly  extricated,  so  as  not  to  be  broken  and 
cause  the  embryos  to  be  scattered  under  the  skin  of  the  host. 
Carter  regards  a  small  worm  ( Urolabes  palustris)  frequent  in 
brackish  water,  as  the  immature  form  of  the  Guinea-worm. 
It  is  also  believed  that  the  embryos  enter  the  bodies  of  water- 
fleas  (Cyclops,  etc.),  and  there  moult,  and  that  consequently 
they  may  be  introduced  into  the  body  by  drinking  standing 
water  ;  but  this  has  not  been  proved.  Other  species  live  in  the 
peritoneum  of  the  horse  and  apes,  and  an  immature  species 
(Filarla  lent  is)  has  been  found  in  the  lens  of  the  human 
eye.  Filarla  sanyuiuis-hominis  is  a  worm  of  microscopic 
size  found  living  in  the  blood  of  the  mosquito  in  India  and 
China.  It  is  said  that  the  eggs  are  swallowed  in  the  water 
drunk  by  man,  are  hatched  in  his  intestines,  and  obstruct 
the  smaller  blood-vessels,  causing,  it  is  claimed,  various 
forms  of  elcphantoid  disease,  perhaps  even  leprosy.  The 
mosquito  sucks  up  the  parasite  in  the  blood  of  leprous  pa- 
tients, voiding  the  eggs  in  the  pools  it  frequents.  Filarla 
hematica  lias  occurred  in  the  blood  of  the  foetus  of  a  dog 
whose  heart  was  tilled  with  them.  Ears  of  wheat  are 
often  infested  by  a  minute  Nematode  (Tylenclius  scandens 

Schneider,  Anguil- 
lula  tritici  of  Need- 
ham,  Fig.  118). 
Other  species  live  in 
flowers,  moist  earth, 
and  sour  decaying 
substances.  Anyuil- 
lula  acetl  Ehren- 
bcrg  is  from  one  to 
two  millimetres  in 
length,  and  lives  in 


Fig.  118.— Young  Wheat-Worm,  greatly  magnifier!. 
</,  section  of  "  cheat**  exhibiting  some  worm?  and  multi- 
tudes ot  eggs,  magnified  :  6,  an  egg  containing  a  worm 
ready  to  hatch.- From  Curtis,  after  Bauer. 


The  genus  Chcelo- 
soma  lives  free  in 
the  sea,  and  has  a  broad  swollen  head  beset  with  fine  hairs. 
It  apparently  connects  the  true  Nematodes  with  Sagitta. 


THE  HAIR-WORMS. 


171 


The  second  suborder,  Gordiacea  or  hair-worms,  differ  in 
their  mode  of  development  from  the  true  Nematode  worms, 
the  embryo  of  Gordius  being  armed  with  oval  spines,  thus 


Fig.  119.— Gordius  aquaticus.  A,  cgc: ;  B,  egg  undergoing  segmentation  of  the 
yolk ;  C,  embryo  (gastrula)  with  the  primitive  stomach,  an  infold  of  the  outer  ger- 
minal layer  of  cells  (ectoderm) ;  D.  embryo  farther  advanced  ;  E,  larva,  with  the 
three  circles  of  spines  retracted  within  the  oesophagus;  F,  the  same  stage  greatly 
enlarged  to  show  the  internal  organs ;  c,  middle  circle  of  spines,  the  head  being 
retracted;  m,  muscular  layei  (?) ;  t,  beak  or  proboscis;  i,  intestine  ;  z.  z,  embryonal 
cells ;  /,  excretory  tube  leading  from  </,  the  secretory  glands ;  on,  oesophagus ;  ?;,  rec- 
tum;  11,  anus.  G,  the  second  larva,  encysted  m  a  fish— (after  Villot).  H,  Gordius 
varius,  end  of  body  of  male,  much  enlarged.  1,  Gordius  aquaticus,  end  of  body 
of  male,  much  enlarged.  K,  (iordins  aquaticus,  natural  size.— (LJ,  I,  K,  drawn  from 
nature  by  J.  S.  Kiugsley.) 

reminding  us  in  this  respect  of  Echinorhyncli-i,  but  the  em- 
bryos, larva?  and  adult  have  a  well-developed  alimentary 
canal. 


172  ZOOLOGY. 

The  hair-worms  belong  to  the  genera  Mermis  and  Gordius. 
In  the  former  genus  the  head  is  beset  with  papillae,  and  the 
end  of  the  body  of  the  male  is  undivided,  while  the  oviduct 
of  the  female  opens  in  the  middle  of  the  body.  The  larva 
is  unarmed  and  has  no  metamorphosis.  Mermis  acuminate 
Leidy  is  pale  brown  and  parasitic  in  the  body  of  the  cater- 
pillar of  the  coddling  moth  ;  another  species  lives  in  the 
bodies  of  grasshoppers. 

The  true  hair-worm,  Gordiits,  has  no  papillae  on  the  head, 
and  the  tail  of  the  male  is  forked,  while  the  oviduct  of  the 
female  opens  at  the  end  of  the  body.  The  following  account 
of  the  development  of  the  common  Gordius  aquaticus  Li  an. 
which  is  a  parasite  of  the  locust  and  other  insects,  and  is 
common  to  Europe  and  this  country,  is  taken  from  Villot's 
"Monographic  des  Dragonneaux." 

The  eggs  (Fig.  119,  A)  are  laid  in  long  chains ;  they  are 
white,  and  excessively  numerous.  The  yolk  undergoes  total 
segmentation  (Fig.  119,  B).  At  the  close  of  this  period, 
when  the  yolk  is  surrounded  by  a  layer  of  cells,  the  germ 
elongates  at  what  is  destined  to  be  the  head-end  ;  this  layer 
pushes  in,  forming  a  cavity,  and  in  this  stage  it  is  called  a 
"gastrula"  (6").  By  this  time  the  embryo  becomes  pear- 
shaped  (D)  •  then  it  elongates.  Subsequently  the  internal 
organs  of  digestion  are  formed,  together  with  three  sets  of 
stiff,  spine-like  appendages  to  the  head,  while  the  body  is 
divided  by  cross-lines  into  segments.  The  head  lies  retracted 
within  the  body  (E). 

In  hatching,  it  pierces  the  egg  membrane  by  the  aid  of  its 
cephalic  armature,  and  escapes  into  the  water,  where  it  passes 
the  early  part  of  its  life.  Fig.  119,  F,  represents  the  embryo  of 
Gordius  aquaticus  greatly  magnified.  It  will  be  seen  how 
greatly  it  differs  from  the  adult  hair-worm,  having  in  this 
stage  some  resemblance  to  the  Acanthocephalus  by  its  cephalic 
armature,  to  the  Nematoidea  or  thread-worms  by  its  alimen- 
tary canal,  and  in  the  nature  of  its  secretory  glands  to  the 
larvae  (cercaria)  of  the  Trematodes  or  fluke-worms.  But  the 
hair-worm  differs  from  all  these  worms  and  even  Mermis,  a 
hair-worm  much  like  and  easily  confounded  with  Gordius, 
in  having  a  complete  metamorphosis  after  leaving  the  egg. 


DEVELOPMENT  OF  HAIR-WORMS.  173 

When  in  this  stage  it  incessantly  protrudes  and  retracts 
its  armed  head,  the  spines  being  directed  backward  when  the 
head  is  out. 

In  the  first  period  of  larval  life  the  worm  lives  encysted 
in  the  bodies  of  aquatic  fly  larvae.  The  vessel  in  which 
M.  Yillot  put  his  Gordius  eggs  also  contained  the  larvae  of 
Tanapus,  Corethra,  and  Chironomus,  small  gnat-like  flies. 
He  found  that  each  of  these  larvae  contained  numerous  cysts 
with  larvae  of  Gordius.  He  then  removed  the  larvae 
from  the  cysts,  placed  them  on  the  gnat-larva,  and  saw  the 
larval  hair-worm  work  its  way  into  the  head  of  the  gnat- 
larva  through  the  softer  part  of  the  integument ;  during  the 
process  the  spines  on  the  head,  reversing  their  usual  position, 
enabled  the  worm  to  retain  its  position  and  penetrate  farther 
in.  Then,  finding  a  suitable  place,  it  came  to  rest,  and  re- 
mained immovable.  Then  the  fluids  bathing  the  parts  co- 
agulated and  formed  a  hard,  granulated  sac.  Tin's  sac  at 
first  closely  envelopes  the  body,  then  it  becomes  looser  and 
longer,  the  worm  living  in  the  anterior  part,  the  front  end 
of  the  sac  being  probably  never  closed.  In  this  first  larval 
state  the  worm  is.  active. 

In  the  second  larval  period  the  young  hair-worm  lives  mo- 
tionless and  encysted  in  the  mucous  layer  of  the  intestines 
of  such  small  fish  as  prey  on  the  gnat-larvae.  A  minnow,  for 
example,  swallowing  one  of  the  aquatic  gnat-larvae,  the  en- 
cysted larva  becomes  set  free  by  the  process  of  digestion  in  the 
stomach  of  the  fish ;  the  cyst  dissolving,  the  young  hair- 
worm itself  becomes  free  in  the  intestine  of  its  new  host. 
Immediately  it  begins  to  bore,  aided  by  the  spines  around 
the  head,  into  the  mucous  membrane  lining  the  inner  wall 
of  the  intestine  of  the  fish,  and  there  becomes  encysted,  the 
worm  itself  lying  motionless  in  its  new  home,  with  its  head 
retracted  and  the  tail  rolled  in  a  spiral.  The  cyst  is  either 
spherical  or  oval.  (Fig.  119,  G.) 

The  return  to  a  free  state  and  an  aquatic  life  occurs  in  the 
spring,  five  or  six  months  after  the  second  encystment.  It 
then  bores  through  its  cyst,  and  passes  into  the  intestinal 
cavity  of  the  fish,  and  from  thence  is  carried  out  with  the 
f^ces  into  the  water.  On  contact  with  the  water  great 


174  ZOO  LOOT. 

changes  take  place.  The  numerous  transverse  folds  in  the 
body  disappear,  and  it  becomes  twice  as  long  as  before,  its 
head-armature  disappears,  the  body  becomes  swollen,  milky, 
and  pulpy.  It  remains  immovable  in  the  water  for  a  vari- 
able period,  and  then  increases  in  size  ;  the  integument  grows 
harder,  and  when  about  two  inches  long  it  turns  brown  and 
begins  to  move.  Most  hair-worms  live  in  ground  beetles 
and  locusts,  twining  round  the  intestines  of  their  host, 
finally  passing  out  of  the  anus.  They  are  often  seen  in 
fresh  water  pools,  twisted  into  knots,  whence  their  name 
Gordius.  They  sometimes  occur  in  horse-troughs,  whence 
they  arc  supposed  by  the  ignorant  to  be  transformed  horse- 
hairs. 

Order  3.  dialog nathi. — This  group  is  represented  by  a 
single  genus,  Sagitta,  which,  from  the  singularities  in  its  form 
and  structure,  has  by  different  authors  been  referred  to  the 
Crustacea,  the  Mollusca  and  even  the  Vertebrates.  Its  de- 
velopment and  structure  show  that  it  is  closely  allied  to  the 
Nematode  worms.  It  is  about  two  centimetres  (nearly  one 
half  inch)  in  length,  and  is  found  swimming  at  the  surface 
of  the  ocean  in  different  parts  of  the  world.  The  lateral  and 
caudal  fin-like  expansions  of  the  skin  of  the  end  of  the 
body  gives  it  a  fish-like  appearance.  There  is  a  well-defined 
head,  with  several  curved  spines  on  each  side  of  the  mouth, 
which  serve  as  jaws  ;  besides  these,  at  the  sides  of  the  head 
are  four  sets  of  short,  strong  spines.  In  the  young  Sagitta 
there  are  also  a  few  pairs  of  lateral  spines  behind  the  head, 
but  these  afterwards  disappear.  The  alimentary  canal  forms 
a  straight  tube  terminating  in  a  ventral  opening  near  the 
posterior  fourth  of  the  body.  The  nervous  system  consists 
of  a  brain  from  which  two  nerves  are  distributed  to  the  eyes, 
and  two  lateral  nerves  pass  backward  to  a  large  ventral  gan- 
glion lying  near  the  middle  of  the  body,  from  which  two 
threads  pass  backwards.  The  sexes  are  united  in  the  same 
individual,  the  two  long  tubular  ovaries  communicating  by 
two  long  ciliated  oviducts,  each  with  a  separate  outlet  at  the 
base  of  the  tail.  Behind  the  ovaries  and  anus  are  two  cham- 
bers in  which  the  spermatic  particles  are  developed  from  mass- 
es of  cells  floating  freely  in  the  perivisccral  fluid,  and  escap- 


THE  SAGITTA.  175 

ing  by  a  lateral  duct  on  cacb  side  of  the  tail.     The  egg  passes 
through  a  mornla  and  gastrula  stage  (Fig.  120).     The  prim- 
itive   opening    (a)    afterwards    closes 
and  a  new  opening  is  made  at  the  op- 
posite pole,  which  is  the  permanent    e 
mouth.     The  embryo  is  oval  at  first, 
but  soon  elongates,  and  the  form  of  the  en\ 
adult  is   attained   before   the   Sagitta 
leaves  the  egg.     Sagitta  elegans  Ver- 
rill  is  about  16  millimetres  in  length, 
and  is  common  in  the  waters  of  New     r>s-  120.— Gastmia  of  sa- 

gitta. — After  Kowalevsky. 

England. 


CLASS  II.  —  NEMATELMINTHES. 

Round-bodied  worms,  with  a  dense  integument,  not  jointed  ;  with  an  ali- 
mentary canal  (except  in  Echinorhynchus);  no  water- vascular  or  respira- 
tory system;  the  nervous  system  usually  reduced  to  a  brain  and  two  ner- 
vous threads  passing  along  the  body ;  with  excretory  organs.  The  head 
sometimes  hooked  or  spinulated  ;  and  except  in  EchinorJiynchus  and  Gor- 
diacea  no  metamorphosis,  tlie  young  Jiatching  in  the  farm  of  tJie  adult. 
Mostly  parasitic,  and  usually  bisexual. 

Order  1.  Acanthocephali. — Cylindrical,  with  a  beak  armed  with  hooks, 
without  mouth  or  digestive  tract.  (Echinorhynchus.) 

Order  2.  Nematodes. — Long,  slender,  cylindrical,  with  a  mouth  and 
intestine  ;  but  no  metamorphosis.  Suborder  1.  True  Ne- 
matodes  (Ascaris,  Oxyuris,  Eustrongylus,  Trichocephalus, 
Trichina,  Filaria,  Anguillula,  Echinoderes).  Suborder  2. 
Gordiacea  (Mermis,  Gordius). 

Order  3.  Chaetognathi. — Having  a  well-marked  head,  with  lateral  and 
caudal  fin-like  expansions  of  the  skin  ;  hermaphrodite. 
(Sagitta.) 

Laboratory  Work. — These  worms  are  to  be  mainly  sought  for  in 
the  alimentary  track  of  fishes  and  mammals,  while  Sagitta  may  be 
caught  with  the  tow-net.  They  may  be  studied  with  good  success  be- 
sides the  ordinary  mode  of  dissection,  by  cross-sections  for  the  micro- 
scope. 


176 


ZOOLOGY. 


CLASS  III. — ROTATORIA  (Rotifers). 

General  Characters  of  Rotifers.— The  Rotifers,  or  wheel- 
animalcules,  are  abundant  in  standing  water,  in  damp  moss, 
etc.,  and  in  the  ocean,  and  are  so  transparent  that  their  in- 
ternal anatomy  can  be  studied  without  dissection,  while  they 
are  so  minute,  being  from  one  fortieth  to  three  hundred ths 
of  an  inch  in  length  (J  to  f  mm.),  that  high  powers  of  the 

microscope  are  needed  in 
studying  them.  They  are 
of  special  interest  from 
the  fact  that  after  being 
dried  for  months  to  such 
a  degree  that  little  if  any 
moisture  is  left  in  the 
body,  they  may  be  revived 
and  become  active.  Pro- 
fessor Owen  has  observed 
the  revivification  of  a 
Rotifer  after  having  been 
kept  for  four  years  in  dry 
sand. 

As  an  example  of  the 
ordinary  type  of  Rotifer 
we  may  cite  Squamella 

Fig.  m.-Sqnamella  oblonqa,  magnMed  200  oUonga  (Fig.   121),  which 

diameters.    A  view  from  below;  shell  or  cara-  •       «lljp/|     fn     Ttrncliinmi1* 

pace  (.<?,  s1,  s2) ;  s,  the  anterior  transverse  edge  * 

of  the  carapace  ;  .s1,  the  anterior,  and  ,s-Q,  the  rPT-ip     plinrnptpvi«:fip    nrcran 

posterior  corners  of  the  carapace  ;,sMhe  border  -  .HStlC    Olgan 

of  the :oval,  flat  area  which  occupies  the  lower  of    the    wheel-animalcules 

face  of  the  carapace ;  Ib,  the  cilia-bearing  vclnm  . 

of  the  head;  /,  the  fork  of  the  tail  (/')  ;  m,  the  is   the    VelUlll    (Ib)  or   pair 
mouth  ;  j,  jaws;.;'1,  muscles  which  move  j  ;  at,  -TXT  in-i      n 

stomach  ;  cv,  the  contractile  vesicle,  or  heart  of  OI  Ciliated.  Wheel-like  flaps 
the  excretory  system ;  c?;1,  c?;2,  the  right,  and  ,       .  ,         „     ,       n         , 

cv3,  cv*,  the  left  excretory  vessels  ;  eg,  eg1,  eg"2,  On  each  Side  OI  the  head, 
two  largeiy  developed  young. — After  Clark. 


CQmpamble     to 

the  velum  of  the  larval  mollusk.  By  means  of  the  rotatory 
movements  of  this  velum  the  creature  is  whirled  swiftly 
around.  The  body  is  broad  and  flattened,  with  the  walls 
often  dense,  chitinons,  sometimes  shell-like,  and  variously 
sculptured,  or  the  animal  may  be  long  and  worm-like,  as  in 
Rotifer  vulgaris  (Fig.  122).  The  body  is  composed  of  several. 


STRUCTURE  OF  ROTIFERS. 


m 


not  over  six,  segments.  A  Rotifer  may,  in  fact,  be  regarded 
as  an  advanced  trochosphere  or  more  properly  cephalula,  and 
comparable  with  the  larvas  or  cephalula?  of  mollusks,  Poly- 
zoa,  Brachiopoda  and  the  Annelids.  The  alimentary  canal 
consists  of  a  funnel-like  cavity,  the  mouth,  which  may 
be  central,  or  situated  on  one  side  of  the  head ;  it  leads 
to  the  mastax  or  pharynx-like  muscular  sac,  supporting 
a  complicated  set  of  chitinous  teeth  within  (malleus 
and  incus)  which  seize  and  masticate  the  food,  which, 
through  the  rotary  action  of  the  velum,  passes 
down  the  buccal  channel  or  mouth-opening,  and 
lodges  within  the  mastax.  The  so-called  sali- 
vary glands  arc  two  large,  clear,  vesicular 
glands,  which  are  attached  to  the  funnel  and 
rest  on  the  summit  of  the  mastax.  The  latter 
opens  into  the  oesophagus,  "a  membranous 
tube,  capable  of  great  expansion  and  contraction, 
but  varying  much  in  length  and  diameter  in 
different  genera. "  Gosse  also  states  that  a  cur- 
rent of  water  appears  to  be  almost  constantly 
setting  through  the  funnel  and  mastax,  and 
thence  through  the  oesophagus  into  the  stomach  • 
the  latter  is  quite  large,  and  provided  with  so- 
called  "pancreatic"  glands,  emptying  into  the 
anterior  end.  There  are  also  hepatic  follicles 
and  cueca,  while  the  intestine  ends  in  a  rectum 
and  cloaca,  the  latter  opening  at  the  base  of 
the  tail.  In  Notommata,  the  digestive  canal 
ends  in  a  blind  sac,  and  in  such  male  Rotifers 
as  are  known,  there  is  no  digestive  cavity,  the  pig. 
canal  being  represented  by  a  solid  thread. 

There  are  no  vascular  or  respiratory  organs,  but  Sai^IeJ^J)0 
a  system  of  long,  convoluted  excretory  tubes, 
one  on  each  side  of  the  body,  which,  as  in  the  Trematodes 
and  Cestodes,  unite  in  a  common,  large  contractile  vesicle 
which  opens  into  the  end  of  the  intestine.  These  tubes, 
which  are  in  places  ciliated,  correspond  to  the  segmental  or- 
gans of  Annelids  ;  they  are  open  at  the  end,  the  cavity  of 
the  tubes  thus  communicating  with  the  body-cavity. 


178  ZOOLOGY. 

The  nervous  system  is  very  simple,  consisting  of  a  rather 
large  ganglion  situated  behind  one  wing  of  the  velum,  and 
lying  just  under  an  eye-spot.  A  supposed  organ  of  hearing, 
consisting  of  a  sac  filled  with  calcareous  matter,  is  attached 
to  the  ganglion. 

The  sexes  are  distinct,  and  the  male  and  female  reproduc- 
tive glands  open  into  the  cloaca.  The  sexes  are,  moreover, 
remarkably  unlike,  the  males  being  much  smaller  than  the 
females,  rudimentary,  sac-like  in  form,  without  any  digestive 
sac,  and  are  very  short-lived.  Some  Kotifers  produce  what 
are  called  winter  as  well  as  summer  eggs  ;  the  former  being, 
as  in  some  Turbellarian  worms  and  Polyzoa,  covered  with  a 
hard  shell  to  resist  the  extremes  of  the  winter  temperature. 
The  summer  eggs  develop  without  being  fertilized,  while  the 
winter  eggs  are  fertilized,  those  of  Lacinularia,  however, 
according  to  Huxley,  not  being  impregnated. 

The  eggs  of  Brachionus  are  attached  by  a  stalk  to  the 
hinder  part  of  the  body  of  the  female.  The  following 
remarks  apply  to  the  mode  of  development  of  the  fe- 
male eggs,  which  are  quite  distinguishable  from  the  mas- 
culine ones.  The  eggs  undergo  total  segmentation,  and 
the  outer  layer  of  cells  resulting  from  subdivision  forms 
the  blastoderm,  and  when  this  is  developed  the  forma- 
tion of  the  organs  begins.  The  first  occurrence  is  an  in- 
folding of  the  blastoderm  (ectoderm)  forming  the  primitive 
mouth,  which  remains  permanently  open,  the  mouth  not 
opening  at  the  opposite  end  as  in  Sayiita,  but  the  entire  de- 
velopment of  the  germ  is  much  as  in  the  mollusk  Calyptrcea, 
as  Salensky  often  compares  the  earliest  phases  of  devel- 
opment of  this  Rotifer  with  those  of  that  mollusk.  The 
"trochal  disk,"  or  velum,  arises  in  certain  mollusks, 
as  a  SAvelling  on  each  side  of  the  primitive  infolding. 
There  is  soon  formed  at  the  bottom  of  the  primitive  in- 
folding a  new  hole  or  infolding  of  the  ectoderm,  which  is 
the  true  mouth  and  pharynx,  while  a  swelling  just  behind 
the  mouth  becomes  the  under  lip.  The  stomach  and  intes- 
tine arise  originally  from  the  endoderm. 

Soon  after,  the  two  wings  of  the  velum  become  well 
marked  (Fig.  123,  v),  and  their  relation  to  the  head  is  as 


DEVELOPMENT  OF  ROTIFERS.  179 

constant  as  in  Calyptnea.  The  tail  (/)  becomes  conical, 
larger,  and  the  termination  of  the  intestine  and  anal  open- 
ing is  formed  at  the  base. 

The  internal  organs  are  then  elaborated  ;  first  the  nervous 
system,  consisting  of  but  a  single  pair  of  ganglia  arising 
from  the  outer  germ -layer  (ectoderm).  Soon  after  the  sen- 
sitive hairs  arise  on  the  wings  of  the  velum. 

Fig.  123  represents  the  advanced  embryo,  with  the  body  di- 
vided into  segments,  the  pair  of  ciliated  wings  of  the  velum 
(•t»),  and  the  long  tail  (t).  At  this  time  the  shell  begins  to 
form,  and  afterwards  covers  the  whole  trunk,  but  not  the  head. 

The  inner  organs  are  developed  from  the  inner  germ-layer 
(endoderm),  which  divides  into  three  layers,  one  forming  the 
middle  part  of  the  intestine,  and  the  two  others  the  glands 
and  ovaries.     The  pharyngeal  jaws  arise  as 
two  small  projections  on  the  sides  of  the 
primitive  cavity.      The  male   develops  in 
the  same  mode  as  the  female. 

Though  the  development  of  the  Rotifers, 
so  far  as  known,  is  more  like  that  of  the 
niollusks  than  true  worms,  the  Rotifers 
may  be  regarded  as  a  generalized  cephalula 
form,  representing  the  larval  forms  of  An- 
nelids and  niollusks,  with  decided  affinities,  ncafiy  ready  t<?  hatch! 
when  we  consider  their  chitinous  covering  ~Afte 
or  carapace,  the  fold  of  the  intestine,  and  the  single  nervous 
ganglion,  to  the  Polyzoa,  and  with  more  remote  resemblances 
to  the  Brachiopods.  They  are  on  the  whole  generalized  forms. 
A  few  species  are  parasitic  :  Albertia  living  internally,  and 
Balatro  on  the  surface  of  the  Nais-like  worms.  With  the 
lower  Rotifers  are  associated  a  group  of  worm-like  forms 
represented  by  Ck&tonotus,  Ichtkydium,  etc.,  and  forming 
the  group  Gastrotricha.  They  have  no  mastax,  and  the  body 
is  only  ciliated  near  the  end.  Through  Dinophilus,  a  Tur- 
bellanan  worm,  they  are  connected  with  the  flat  worms. 
The  genus  EcMnoderes  is  also  regarded  by  Glaus  as  a  low 
Rotifer.  It  seems  quite  apparent  from  this  that  the  Rotifers 
are  a  type  which  has  originated  from  worms  resembling  the 
generalized  Tnrbelluriau  form,  and  which  connects  the  latter 


180  ZOOLOGY. 

with  the  Polyzoa,  Bracldopods,  and  possibly  the  Mollusca, 
the  latter  branch  being  probably  a  modified  vermian  type, 
and  with  an  ancestry  not  unlike  that  of  the  Rotifers  and 
aberrant,  generalized  Polyzoa  and  Brackiopoda.  The  classi- 
fication of  the  Rotatoria  is  in  an  unsettled  state,  the  group 
probably  consisting  of  three  orders,  viz.  :  the  true  Rotatoria, 
the  Ecliinoderidce,  and  Gastrotricha, 


CLASS  III. -ROTATORIA. 

Worms  with  usually  moi*e  or  less  solid  segments,  very  unequally  developed, 
bearing  a  ciliated  velum,  the  mouth  opening  into  a  mastax  ;  sexes  separate, 
the  males  much  smaller,  more  rudimentary  than  the  females.  A  small 
nervous  ganglion.  No  circulatory  apparatus,  but  with  a  voluminous  excre- 
tory (icater-vascular)  organ. 

(Albcrtia,  Asplaiichna,  Hydatiua,  Bracldonus,  Rotifer,  and  the 
highest  form,  Floscularia.) 

Laboratory  Work. — The  Rotifers  can  only  be  studied  while  alive  and 
as  transparent  objects.  Little  is  known  about  the  American  species. 


CLASS  IV. — POLYZOA  (Moss  Animals). 

The  Polyzoa,  though  not  commonly  met  with  in  fresh 
water,  are  among  the  commonest  objects  of  the  seashore. 
They  are  minute,  almost  microscopic  creatures,  social,  grow- 
ing in  communities  of  cells  (called  poly- 
zoaria  or  corms),  forming  patches  on  sea- 
weeds and  stones  (Fig.  124,  Membranipora 
solida  Pack.).  Certain  deep-water  species 
grow  in  coral-like  forms  (Fig.  125,  Myrio- 
zoum  subgracile  D'Orbigny),  while  the 
chitinous  or  horny  Polyzoa  (Fig.  126, 
Halopliila  lorealis  Pack.),  are  often  mis- 
Fig.  124.— ceils  of  sea-  taken  for  sea- weeds  on  the  one  hand,  and 
oat,  eDiarged.  gertuiarjan  Hydroids  on  the  other.  From 
their  likeness  to  mosses  the  name  Bryozoa  was  given  to  the 
group  by  Ehrenberg,  a  year  after  Thompson  (1830)  had 
called  them  Polyzoa,  so  that  the  latter  name  has  priority. 


THE  POLTZOA. 


181 


The  simpler  form  of  Polyzoon  is  a  worm-like  creature 
enclosed  in  a  minute,  deep,  horny  cell,  with  the  alimentary 
canal  bent  on  itself  and  terminating  in  a  vent  situated  near 
the  mouth,  the  latter  surrounded,  in  the  fresh-water  forms, 


Fig.  125.— Branching  marine  Polyzoon.    Corm  of  Myriozoum  subgracile, 
natural  size. 

with  a  horseshoe-shaped  crown,  or  in  the  marine  species  a 
circle  of  slender  ciliated  tentacles.  The  animal  when  dis- 
turbed withdraws  into  its  tube  or  shell,  which  is  often  trans- 
parent, allowing  it  to  be  examined 
when  alive.  The  cells  are  rarely 
single,  but  a  cormus,  polyzoarium  or 
polyzoon-stock  is  formed  by  the  bud- 
ding of  numerous  cells  from  the  one 
first  formed.  The  single  polyzoon  is 
called  a  polypide,  and  its  cell  a  cystid. 
In  Pedicellina,  the  simplest  polyzoon, 
the  polypide  has  no  cystid  or  cell. 
The  cells  are,  in  the  marine  forms, 
usually  closed,  and  independent  of 
each  other.  The  wall  forming  the 
cell  is  called  the  endocyst ;  it  com- 
prises the  ectoderm  proper,  with  a  portion  (parietal  layer)  of 
the  mesoderm  forming  the  soft  lining  of  the  cell. 


Fig.  126.—ffalophila  borealis, 
enlarged. 


182 


ZOOLOGY. 


The  mouth  is  situated  on  a  disk  (lophophore,  Fig.  127,  £), 
bearing  the  tentacles,  which  are  hollow  processes  of  the 
body-walls,  communicating  with  the  body-cavity,  the  blood 
flowing  into  them,  there  being  aerated,  while  they  are  exter- 
nally ciliated.  They  serve  both  to  catch  food  and  for  respir- 
ation as  makeshift  gills.  Hyatt  states  that  the  tentacles  are 
used  not  only  to  catch  the  prey,  but  for  a  multitude  of  other 
offices.  They  are  each  capable  of  in- 
dependent motion,  and  may  be  twisted 
or  turned  in  any  direction  ;  bending 
inwards,  they  take  up  and  discard 
objectionable  matter,  or  push  down 
into  the  stomach  and  clear  the 
oesophagus  of  food  too  small  to  be 
acted  upon  by  the  parietal  muscles. 
They  are  also  employed  offensively  in 
striking  an  intrusive  neighbor,  and 
their  tactile  power,  sensitive  to  the 
slightest  unusual  vibration  in  the 
water,  warns  the  polypide  of  the  ap- 
proach of  danger. 

The  digestive  canal  hangs  free  in 
the  body-cavity,  only  attached  by  the 
mouth  and  anus  to  the  walls  of  the 
body.  It  consists  of  a  pharynx,  a 
large  stomach,  and  an  intestine  which 

Fig.  127.— Organization  of  a  lino  hv  thp  dido  nf  fhf  nhnrvnv    9inrp 

Polyzoon.  A,  Paludicella  Eh-  11GS  °J  *  G  Pnaijnx?  s 

renbergn.    B,  PlumateUafru-  the    Canal   has   a    Simple    deep    dorsal 
ticostt.  br,  tentacular  branchiae 

of lophophore; a. .oesophagus;   flexure,    the   vent  being  situated  on 

v,  stomach  ;   r,  n»testine ;   a,  ,  .. .          r, 

anus ;  i,  cell ;  a?,  posterior,  a1,  the  dorsal  or  cardiac  side,  near  the 

anterior  cord,  at  the  insertion  .,          TT        ,,      .,          ,  ,     .     ,.     , 

of  which  into  the  body  the  mouth.     Usually  the  stomach  is  tied 

generative  products  are  devel-    -.  J_J?TV  j_    /  /•       •      -      \  ± 

oped:  i,  testcs :  o,  ovary ;  m,  by  a  sort  of  ligament  (fumcutus)  to 
a  point  on  the  body- walls,  near  the 
mouth.  The  nervous  system  is  rep- 
resented by  a  double  ganglion  form- 
ing a  single  mass  situated  between  the  mouth  and  vent ;  it 
is  highly  contractile  and  changeable  in  form.  There  is  no 
heart  nor  any  circulatory  apparatus.  The  sexes  are  united 
in  a  single  polypide,  the  glands  forming  masses  growing  on 


principal    retractor  muscle.— 
After  Allmun. 


OA     ** 

STRUCTURE  OF  THE  POLYZOA.      '//,»    18/ '/' 

the  f uniculus  or  in  the  walls  of  the  body.  The  body,  \  - 
especially  the  lophophore,  is  retracted  and  pushed  out 
by  muscles  arranged  in  pairs  on  either  side.  As  seen  in 
Fredericclla,  a  fresh-water  form,  the  alimentary  canal 
"hangs  from  the  lophophore,  occupying  the  centre  of 
the  polypide,  and  floating  freely  in  the  rapidly  moving 
blood"  (Hyatt).  The  yellowish  resophagus,  the  stomach 
barred  with  brown,  and  the  brownish  intestine  are  balanced 
upon  a  fold  of  the  intestine  (the  invaginated  fold),  which 
is  retained  in  the  cell  by  the  retentor  muscles,  and  is  sur- 
rounded by  a  large  sphincter  muscle.  There  are  two  sets 
of  large  retractor  muscles,  one  on  each  side  of  the  digestive 
canal,  and  arising  from  two  common  bases  ;  each  large  trunk 
subdivides  into  three  branches,  the  retractor  of  the  stomach, 
of  the  lophophore,  and  of  the  anus.  The  crown  of  tenta- 
cles is  swayed  by  these  muscles  in  every  direction,  or  when 
alarmed  the  polypide  may  withdraw  by  their  aid  into  the 
cell,  as  the  finger  of  a  glove  may  be  inverted  within  the 
empty  palm.  This  may  be  done  with  great  rapidity  or 
slowly.  The  process  has  thus  been  graphically  described  by 
Hyatt :  "  The  polypidal  endocyst  is  first  turned  inwards, 
folding  upon  itself,  and  prolonging  the  permanently  invagi- 
nated fold  below.  The  tentacles,  arriving  at  the  edge  of 
the  coencecial  orifice,  are  pressed  into  a  compact  bundle  by 
the  action  of  their  own  muscles,  and,  together  with  the 
lophophore,  are  dragged  into  the  cell  by  the  continued  invag- 
ination  of  the  endocyst  until  they  are  wholly  enclosed  and 
at  rest  within  the  sheath  formed  for  them  by  the  inverted 
walls  of  the  tube.  The  sphincter  muscle  then  closes  the 
ccenoacial  orifice  above,  and  the  process  of  invagination  is 
completed. 

"  The  polypide  in  its  exserted  state  is  buoyed  up  and  sus- 
tained by  the  pressure  of  the  fluids  within.  Consequently, 
when  invaginated,  it  displaces  an  equal  bulk  of  these  in  the 
closed  coenoacium,  and  their  reaction,  aided  by  the  contrac- 
tion of  the  muscular  endocyst,  is  sufficient  to  evaginate  the 
whole. 

"  The  evagination  begins  with  the  relaxation  of  the  sphinc- 
ter, which  permits  the  ends  of  the  tentacles  to  protrude. 


184  ZOOLOGY. 

These  daintily  feel  about  for  the  cause  of  the  alarm,  and,  if 
they  fail  to  detect  the  proximity  of  an  enemy,  the  whole 
fascicle  is  cautiously  pushed  out,  and  the  sentient  threads 
suddenly  and  confidently  unfolded. 

"  The  polyzoon  reasons  from  the  sense  of  touch  inherent 
in  its  tentacles,  and  cannot  be  induced  to  expose  itself  above 
the  ccencecium  until  thoroughly  satisfied  by  these  sensitive 
feelers  that  no  danger  is  to  be  apprehended.  In  fact,  these 
plant-like  creatures,  singly  mere  pouches  with  a  stomach 
hanging  in  the  midst,  exhibit  greater  nervous  activity  and 
'animality,'  than  we  find  among  the  more  highly  organized 
Ascidia,  or  shell -covered  Brachiopoda." 

The  epistome  is  a  fold  of  the  lophophore,  used  to  close  the 
mouth  and  thus  prevent  the  food  from  escaping  from  the 
mouth.  It  is  tongue-like  and  very  pliable.  "  The  border  is 
capable  of  a  tactile  motion  similar  to  that  of  the  human 
tongue,  and  it  takes  cognizance  of  what  passes  into  the 
mouth  by  frequent  and  repeated  jerks  toward  the  aperture" 
(Hyatt).  It  is  situated  immediately  over  the  ganglionic  mass, 
and  between  the  anus  and  mouth. 

The  Polyzoa,  as  regarded  by  Hyatt  and  others,  are  struc- 
turally nearly  related  to  the  Brachiopods,  the  higher  forms 
of  which,  such  as  Terebratula  and  Rhynconella,  have  the  res- 
piratory tentacles  similarly  placed  around  the  disk  or  lopho- 
phore, which  is  perforated  at  the  centre  by  the  mouth,  and 
from  which  the  alimentary  canal  hangs,  with  a  dorsal  flexure 
and  anus  near  the  mouth.  "  The  extension  of  the  lophophore 
into  two  or  three  spiriforrn  arms,  the  complex  structure  of 
the  tentacles  and  of  the  muscular  and  nervous  systems,  are 
all  more  or  less  foreshadowed  by  the  condition  of  these  sys- 
tems among  the  higher  Polyzoa."  On  the  other  hand,  the 
Polyzoa  are  closely  related  to  the  worms,  the  Gephyrean 
worm,  Phoronis,  being  the  connecting  link.  The  mode  of 
development  of  the  Polyzoa  and  Brachiopoda  are  quite  simi- 
lar, as  will  be  seen  farther  on,  and  owing  to  these  decided  sim- 
larities  in  development  and  anatomy,  the  Polyzoa  and  Brachi- 
opods form  a  natural  group  or  series,  distinct  on  the  one 
hand  from  the  Rotatoria,  and  on  the  other  from  the  mollusks 
and  worms. 


DEVELOPMENT  OF  THE  POLYZOA.  185 

Certain  brandling  marine  forms  are  provided  with  organs 
like  birds' heads,  situated  on  a  stalk  and  called  avicularia,  with 
a  movable  jaw-like  appendage,  which  keeps  up  an  incessant 
snapping.  Beside  the  avicularia,  there  are,  as  in  Scrupo- 
cellaria,  long  bristle-like  appendages  to  the  cells,  called 
vibracula. 

There  are  no  organs  of  special  sense  in  the  Polyzoa,  unless 
the  epistome  maybe  legarded  as  an  organ  of  sense,  and  the 
nervous  system  consists  of  a  single  rounded  ganglion  (Frede- 
ricella),  or,  as  in  Plumatella,  a  double  ganglion,  situated  be- 
tween the  mouth  and  vent,  from  which  one  set  of  nerves  are 
distributed  to  the  epistome,  lophophore,  tentacles,  and  evagi- 
nable  endocyst,  and  another  set  to  the  various  parts  of  the  ali- 
mentary canal.  A  so-called  colonial  nervous  system  is  sup- 
posed to  exist  in  the  Polyzoa,  as  when  the  coencecium  in  some 
forms  is  touched  all  the  polypides  become  alarmed,  which 
indicates  that  a  set  of  nerves  connect  the  different  polypides, 
though  no  such  nerves  have  yet  been  discovered.  The 
fresh-water  Polyzoa  are  not  sensitive  to  light,  nor  to  noises, 
only  to  agitation  of  the  water  in  which  they  dwell. 

All  the  Polyzoa  are  hermaphrodite,  the  ovary  and  male 
glands  residing  in  the  same  cystid,  the  testis  being  situated 
near  the  bottom  and  attached  to  the  funiculus,  while  the 
ovary  is  attached  to  the  Avails  of  the  upper  part  of  the  cell. 

Allman  regards  the  polypide  and  cystid  as  separate  indi- 
viduals. The  singular  genus  Loxosoma  is  like  the  polypide 
of  an  ordinary  Polyzoan,  but  does  not  live  in  a  cell  (cystid). 
On  the  other  hand,  we  know  of  no  cystids  which  are  with- 
out a  polypide.  Remembering  that  the  cystids  stand  in  the 
same  relation  to  the  polypides  as  the  hydroids  to  the  medusae, 
as  Nitsche  insists,  we  may  regard  the  polypides  as  secondary 
individuals,  produced  by  budding  from  the  cystids.  The 
large  masses  of  cells  forming  the  moss-animal,  which  is  thus 
a  compound  animal,  like  a  coral  stock,  arises  by  budding  out 
from  a  primary  cell.  The  budding  process  begins  in  the 
endocyst,  or  inner  of  the  double  walls  of  the  body  of  the 
cystid,  according  to  Nitsche,  but  according  to  an  earlier 
Swedish  observer,  F.  A.  Smitt,  from  certain  fat  bodies  float- 
ing in  the  cystid. 


186  ZOOLOGY. 

The  Polyzoa  are  divided  primarily  into  the  Entoprocta, 
represented  by  Loxosoma  alone,  in  which  the  vent  is  situated 
within  the  circle  of  tentacles,  and  the  Ectoprocta,  in  which 
the  vent  lies  outside  of  the  lophophore — a  group  comprising 
all  the  higher  Polyzoa  (Gymnolmmata  and  Pliylactolcemata). 

The  development  of  the  Polyzoa  is  not  very  complicated. 
In  the  marine  forms,  as  studied  by  Barrois,  the  germ  passes 
through  a  morula  stage  ;  after  which  the  cells  are  arranged 
into  two  halves,  separated  by  a  crown  of  cilia  ;  at  this  stage 
it  is  called  a  Uastula.  At  the  time  of  birth  the  ciliated  germ 
is  a  disk-shaped  gastrula,  with  two  opposite  faces  or  ends, 
separated  by  the  croAvn,  one  (aboral)  bearing  in  its  centre 
the  mouth-opening.  This  ciliated  free-swimming  top-like 
gastrula  stage  is  called  a  trocho  sphere. 

After  swimming  about  as  ciliated  larvae  (trochospheres), 
the  shell  or  ectocyst  develops,  and  the  larva  becoming  station- 
ary, the  cystid  forms,  its  calcareous  shell  develops,  and  finally 
the  polypide  is  indicated,  and  the  primitive  cell  is  gradually 
formed. 

As  seen  m  Phalanyella  flalellanz,  the  larva,  after  becoming 
fixed  to  some  object,  consists  of  a  white  pyriform  mass, 
closely  enveloped  by  an  ectocyst,  with  numerous  fat  globules 
between  the  latter  and  the  white  mass.  The  ectocyst  swells 
into  a  discoidal  sac,  with  endocyst,  ectocyst,  and  an  external 
zone,  while  the  internal  whitish  mass  transforms  into  the 
polypide.  The  discoidal  sac  formed  by  the  endocyst  consti- 
tutes simply  the  basal  disk  of  the  primitive  cell.  The  future 
opening  of  the  cell  appears  on  the  upper  surface  of  the  cell. 
The  budding  out  of  the  secondary  cells  of  the  polyzoarium 
or  corm  then  takes  place.  It  begins  by  the  appearance  of  a 
cell  placed  in  front  and  below  the  primitive  cell,  and  which 
borders  it  on  each  side  ;  its  secondary  cell  then  divides  into 
two,  each  of  which  successively  gives  origin  to  three  cells, 
and  we  thus  arrive  at  an  Idmonea  stage  ;  and  finally  the 
Phalangella  stage  is  reached,  the  process  being  a  dichoto- 
mous  mode  of  budding  quite  analogous  to  that  which  pro- 
duces the  broad,  flattened  corm  of  Escliarina. 

The  development  of  Membranipora  pilosa,  which  is  very 
abundant  on  our  shores,  growing  on  sea-weeds,  is  of  singu- 


DEVELOPMENT   OF  THE  POLYZOA.  187 

lar  interest.  The  free-swimming  ciliated  larva  is  provided 
with  a  bivalve  shell,  and  was  originally  described  as  a  La- 
mellibrancli  larva  under  the  name  of  CypJionautes. 
Schneider  discovered  that  it  was  a  young  Membranipora. 
Barrois,  who  has  traced  its  complete  history,  states  that  its 
metamorphosis  is  fundamentally  like  that  of  the  other  ma- 
rine Polyzoa.  Flustrella  Mspida  passes  through  a  similar 
Cyphonautes  stage. 

In  Loxosoma  young  resembling  the  adult  bud  out  like 
polyps.  Nitsche  does  not  regard  this  budding  process  as  an 
alternation  of  generations,  but  states  that  in  Polyzoa  of  the 
family  of  Vesicular iidce,  this  may  occur,  as  in  the  latter 
some  cystids  form  the  stem,  and  others  (the  zocecia)  produce 
the  eggs.  Most  fresh-water  Polyzoa  reproduce  by  the  devel- 
opment of  winter  buds  or  eggs  surrounded  by  a  horny  case, 
and  developing  from  the  funiculus. 

To  recapitulate  :  the  Polyzoa  increase  (a)  by  budding  ;  (b) 
by  normal  (summer)  eggs,  and  by  producing  statoblasts,  or 
winter  eggs.  In  reproducing  from  summer  eggs,  the  young 
pass  successively  through  a  morula,  blastula,  gastrula  and 
trochosphere  stage  before  attaining  maturity. 

The  most  aberrant  Polyzoan  is  RUdbdopleura  mirdbilis  Sars, 
which  occurs  in  from  100  to  300  fathoms  on  the  coast  of 
Norway.  It  differs  from  other  forms  by  the  want  of  an  en- 
docyst  or  mantle,  whence  it  moves  up  and  down  in  its  cell, 
without  being  attached  to  the  opening,  the  muscles  usually 
present  being  wanting,  the  cord  by  which  it  is  attached  to 
the  bottom  of  its  long,  slender  tubular  cell  being  contractile. 
The  lophophore  is  much  like  that  of  the  fresh-water  Poly- 
zoans,  consisting  of  two  long  arms,  bearing  two  rows  of 
slender  tentacles.  The  cpistome  is  represented  by  a  large 
round  disk. 

The  marine  Polyzoa  occur  at  great  depths,  and  a  few  species 
are  cosmopolitan;  the  type  is  very  persistent,  and  occurs 
in  the  oldest  Silurian  strata,  the  earliest  forms  being  very 
similar  to  their  living  descendants. 


188  ZOOLOGY. 

CLASS  IV.— POLYZOA. 

Animals  usually  forming  moss-like  or  coral-like  calcareous  or  chitinous 
masses  called  corms,  each  cell  containing  a  worm-like  animal,  with  the  di- 
gestive tract  flexed,  the  anus  situated  near  the  mouth.  T/ie  body  usually 
drawn  in  and  out  oftlie  cell  by  the  action  of  retractor  and  adductor  muscles. 
Tlie  mouth  surrounded  by  a  crown  of  long  tentacles.  No  heart  or  vascular 
system.  Nervous  system  consisting  of  a  single  or  double  ganglion  situated 
between  the  mouth  and  vent,  with  nerves  proceeding  from  it.  Hermaphro- 
ditic ;  multiplying  by  budding  or  eggs.  Tlie  embryo  passing  through  a 
morula,  gastrula  and  trocJiosphere  stage,  the  corm  being  formed  by  the 
budding  of  numerous  cells  from  a  primitive  one. 

Order  1.  Entoprocta. — Vent  within  the  lophophore.    (Loxosoma.) 

Order  2.  Ectoprocta. — Vent  without  the  lophophore.    (Lepralia,   Es- 
chara,  Idmonea,  Myriozoum.) 

Laboratory  Work. — The  Polyzoa  are  too  small  to  dissect,  and 
must  be  studied  while  alive  as  transparent  objects,  and  may  be  kept 
in  aquaria.  The  corms  in  part  or  whole  can  be  mounted  for  the  mi- 
croscope as  opaque  objects. 


CLASS  Y. — BRACHIOPODA  (Lamp  Shells). 

General  Characters  of  Brachiopods.— This  group  is  named 
Bracliiopoda  from,  the  feet-like  arms,  fringed  with  tentacles, 
coiled  up  within  the  shell,  and  which  correspond  to  the 
lophophore  of  the  Polyzoa  and  the  crown  of  tentacles  of  the 
Sabella-like  worms.  From  the  fact  that  the  animal  secretes 
a  true,  bivalved,  solid  shell,  though  it  is  usually  inequivalve, 
i.  e.,  the  valves  of  different  sizes,  the  Bracldopoda  were  gener- 
ally, and  still  are  by  some  authors,  considered  to  be  mol- 
lusks,  though  aberrant  in  type.  They  may  be  regarded  as  a 
synthetic  type  of  worms,  with  some  superficial  molluscan 
features.  The  shell  of  our  common  northern  species,  Tere- 
Iratulina  septentrionalis,  which  lives  attached  to  rocks  in 
from  ten  to  fifty  or  more  fathoms  north  of  Cape  Cod,  is  in 
shape  somewhat  like  an  ancient  Roman  lamp,  the  upper  and 
larger  valve  being  perforated  at  the  base  for  the  passage 
through  it  of  a  peduncle  by  which  the  animal  is  attached 
to  rocks.  The  shell  is  secreted  by  the  skin  (ectoderm),  and  is 


STRUCTURE  OF  BRACHIOPODS.  189 

composed  of  carbonate  (Terebratulina)  or  largely  (Lingula, 
Fig.  133)  of  phosphate  of  lime.  It  is  really  the  thickened 
integument  of  the  animal,  the  so-called  mantle  being  the 
inner  portion  of  the  skin,  containing  minute  tubular  canals 
which  do  not  open  externally. 

The  body  of  Brachiopods  is  divided  into  two  parts,  the 
anterior  or  thoracic,  comprising  the  main  body-cavity  in 
which  the  arms  and  viscera  are  contained,  and  the  caudal 
portion,  i.  c.  the  peduncle.  The  part  of  the  body  in  which 
the  viscera  lodge  is  rather  small  in  proportion  to  the  entire 
animal,  the  interior  of  the  shell  being  lined  with  two  broad 
lobes,  the  free  edges  of  which  are  thickened  and  bear  setae, 
as  seen  distinctly  in  Lingula.  The  body-cavity  is  closed 
anteriorly  by  a  membrane  which  separates  it  from  the  space 
in  which  the  arms  are  coiled  up.  The  "pallial  cham- 
ber" is  situated  between  the  two  lobes  of  the  mantle  (pal- 
lium] and  in  front  of  the  membrane  forming  the  anterior 
wall  of  the  body-cavity.  In  the  middle  of  this  pallial 
chamber  the  mouth  opens,  bounded  on  each  side  by  the 
base  of  the  arms.  The  latter  arise  from  a  cartilaginous 
base,  and  bear  ciliated  tentacles,  much  as  in  the  worm  Sa- 
lella.  In  Lingula,  Discina,  and  Tthynconella,  they  are  de- 
veloped, as  stated  by  Morse,  in  a  closely-wound  spiral,  as  in 
the  genuine  worms  (Amphitrite).  In  Lingula  the  arms  can 
be  partially  unwound,  while  in  Rhynconclla  they  can  not 
only  be  unwound  but  protruded  from  tho  pallial  chamber. 
In  many  recent  and  fossil  forms  the  arms  are  supported  by 
loop-like  solid  processes  of  the  dorsal  valve  of  the  shell,  but 
when  these  processes  are  present  the  arms  cannot  be  pro- 
truded beyond  the  shell.  The  tentacles  or  cirri  on  the  arms 
are  used  to  convey  to  the  mouth  particles  of  food,  and  they 
also  are  respiratory  in  function,  there  being  a  rapid  circula- 
tion of  blood  in  each  tentacle,  which  is  hollow,  communi- 
cating with  the  blood-sinus  or  hollow  in  each  arm,  the  sinus 
ending  in  a  sac  on  each  side  of  the  mouth. 

The  digestive  system  consists  of  a  mouth,  oesophagus, 
stomach,  with  a  liver-mass  on  each  side,  and  an  intestine. 
Fig.  128  shows  the  relation  of  the  mouth  and  digestive  canal 
to  the  head  and  arms,  as  seen  in  a  longitudinal  section  of 


190 


ZOOLOGY. 


the  anterior  part  of  the  body  of  Lingula.  The  mouth  is 
bordered  by  two  membranous,  highly  sensitive  and  movable 
lips.  The  stomach  is  a  simple  dilatation  of  the  alimentary 
canal,  into  which  empty  the  short  ducts  of  the  liver,  which 

is  composed  of 
masses  of  co3ca. 
The  liver  origi- 
nally arises  as 
two  diverticula 
or  offshoots  of 
the  stomach. 
The  short  in- 


testine ends  in 
a  blind  sac  or 
in  a  vent,  and 
is,  with  the 


ft  a 

Fig.  128 — Longitudinal  section  of  the  anterior  portion  of 


Lingula.   m,  mouth ;  CK.  cesophairu^  :  *?/,  stomach  ;  a,  arm  ;  ci,    Stomach,freely 
cirri ;   bf,  brachial  ibid  ;  cb,  cartilaginous  base  of  arm  ;   $,  11* 

pinus  leading  to  the  arm;  cc,  cephalic  collar  or  pallial  mem-    Suspended.     111 

theperivisceral 

cavity  by  delicate  membranes  springing  from  the  walls  of  the 
body.  (Fig.  129.)  In  those  Brachiopods  allied  to  Terebra- 
tula,  Terebratulina,  Thecidium,  Waldheimia,  Rhynconella, 
etc.,  the  stomach  ends  in  a  blind  sac,  and  there  is  no  vent, 
the  rejectamenta  escaping  from  the  mouth.  In  Lingula  and 
Distina  there  is  a  vent  which  terminates  anteriorly  on  the 
right  side.  In  Lingula 
the  intestine  makes  a 
few  turns,  while  in  Dis- 
cina  it  makes  a  single 
turn  to  the  right. 

The   nervous    system 
consists    of    two    small 


Fig.  129. — Transverse  section  of  Lingula.  b, 
bands  suspending  the  intestine  in  the  perivisce- 
ral  cavity  ;  i,  intestine  ;  .«,  segment  al  organ  ;  0, 
ovaries  ;  I,  liver  ;  ft,  gills  ;  se,  setie.— After 
Morse. 


ganglia  above,   and   an 

infraoesophageal  pair  of 

larger  ganglia,  and  there 

are  two  elongated  ganglia  behind  the  arms,  from  which  nerves 

are  given  off  to  the  dorsal  or  anterior  lobe  of  the  mantle. 

From  the  infraoesophageal  ganglia  two  lateral  ventral  cords 

pass  backwards,  in  their  tract  sending  off  delicate  threads, 


STRUCTURE  OF  BRACHIOPODS.  191 

but  with  no  ganglionic  enlargements,  except  in  Distinct, 
where  they  terminate  each  by  a  ganglion  in  the  last  two 
posterior  muscles.  Morse  has  discovered  the  presence  of 
auditory  capsules  in  Lingula. 

Respiration  is  mainly  carried  on  in  the  mantle  (pallial 
membrane).  In  Lingula  the  pallial  membrane  is  divided 
into  oblique  transverse  sinuses,  which 
run  parallel  to  each  other.  From 
these  arise,  says  Morse,  numerous 
flattened  ampullae,  which  are  highly 
Fig.  lao-Ampuii*  of  blood  contractile.  The  blood  courses  in 
sinu-es,  showing  course  taken  regular  order  up  and  down  these 

by  the  blood.— After  Morse.          .  °  l 

sinuses,  entering  each  01  the  ampullae 

in  turn.  Fig.  130  represents  a  row  of  five  ampullae  with  in- 
dications of  the  course  taken  by  the  blood-disks.  These 
ampullae  have  not  been  found  in  Distinct,  though  the  pallial 
sinuses  are  very  prominent.  The  breathing  process  is  also 
carried  on  in  the  tentacles  or  cirri. 

Intimately  connected  with  the  vascular  system  is  a  gland- 
ular portion  of  the  tubular  part  of  the  segmental  organs  of 
the  Bracliiopoda,  which  is 
supposed  to  represent  simi- 
lar parts  in  worms  as  well 
as  the  glandular,  excretory 
portion  of  the  organ  of 
Bojanus  in  mollusks,  and  is 
supposed  to  be  depuratory 
or  renal  in  function. 

The  reproductive  system 
of  Bracliiopoda  consists  of 
ovaries,  oviducts  or  seg- 

,„<.„!  T7I-         -101          Fie.  131.— Segmental  organs  of   Brachio- 

mental     Organs,     Jblg.     131,    pod*   a   Discina ;  b,  Terebratuliua.-After 


and  spermaries.     The  sexes 


po 
Me 


are  probably  separate  in  all  Bracliiopoda  (Morse). 

The  ovaries  are  attached  in  Distinct  and  Lingula  to  the 
delicate  vascular  membranes  of  the  large  sinuses  in  the  pal- 
lial membranes,  the  vascular  membranes  being  thrown  into 
conspicuous  ruffs  when  the  eggs  are  ripe.  In  Terebratulina 
and  Rynchonella  they  are  not  only  similarly  situated,  but 


192  ZOOLOGY. 

hang  in  clusters  from  the  genital  bands  in  the  perivisceral 
cavity.  The  mature  eggs  detach  themselves  from  the  ovary 
to  float  freely  in  the  perivisceral  cavity,  whence  they  pass  into 
the  flaring,  ciliated  mouths  of  the  segmcntal  organs,  and  are 
discharged  by  them  into  the  water.  These  segmental  organs 
or  oviducts  are  tubular,  trumpet-shaped,  as  in  the  true 
worms  (Fig.  131).  In  Lingula,  Discina,  and  Terebratulina, 
there  is  but  a  single  pair,  in  Rhynconella  two  pairs.  The 
external  orifices  of  the  oviducts  form  simple  slits,  while  in 
Terebratulina  they  project  from  the  anterior  walls  like 
tubercles,  as  in  the  true  Avorms  (Morse).  The  spermaries 
occur  in  the  same  situation  in  the  perivisceral  cavity  as  the 
ovaries.  As  observed  in  Terebratulina,  by  Morse,  in  a  few 
hours  after  the  eggs  are  discharged  the  embryos  hatch  and 
become  clothed  with  cilia.  Kowalevsky  observed  in  the  egg 
of  Thecidium  the  total  segmentation  of  the  yolk  (also  ob- 
served in  Terebratulina  by  Morse),  until  a  blastoderm  is 
formed  around  the  central  segmentation  cavity,  which  con- 
tains a  few  cells.  The  similar  formation  of  the  blastoderm 
was  seen  in  Aryiope,  but  not  the  morula  stage.  After  this 
the  ectoderm  invaginates  and  a  cavity  is  formed,  opening 
externally  by  a  primitive  mouth.  The  walls  of  this  cavity 
now  consist  of  an  inner  and  outer  layer  (the  endoderm  and 
ectoderm).  This  cavity  eventually  becomes  the  digestive 
cavity  of  the  mature  animal. 

In  Terebratulina   Morse  observed  that  the  oval  ciliated 
germ  became  segmented,  dividing  into  two  and  then  three 

rings,  with  a  tuft  of 
long  cilia  on  the  an- 
terior end  (Fig.  132, 
A).  In  this  stage  the 
larva  is  quite  active, 
swimming  rapidly 
about  in  every  direc- 

Fig.  132.— Larval  stages  of  Terebratulina.—          tion. 

Soon  after,  the  germ 

looses  its  cilia  and  becomes  attached  at  one  end  as  in  Fig. 
132,  B  (c,  cephalic  segment ;  th,  thoracic  segment ;  p,  pe- 
duncular or  caudal  segment).  The  thoracic  ring  now  in- 


DEVELOPMENT  OF  BRACHIOPODS.  193 

creases  much  in  size  so  as  to  partially  enclose  the  cephalic 
segment,  as  at  C.  The  form  of  the  Brachiopod  is  then  soon 
attained,  as  seen  in  D,  in  which  the  head  (c)  is  seen  project- 
ing from  the  two  valves  of  the  shell  (th),  the  larger  being 
the  ventral  plate. 

The  hinge  margin  is  broad  and  slightly  rounded  when 
looked  at  from  above  ;  a  side  view,  however,  presents  a  wide 
and  flattened  area,  as  is  shown  in  some  species  of  Spirifer, 
and  the  embryo  for  a  long  time  takes  the  position  that  the 
Spirifer  must  have  assumed  (Morse).  Before  the  folds  have 
closed  over  the  head,  four  bundles  of  bristles  appear  ;  these 
bristles  are  delicately  barbed  like  those  of  larval  worms. 
The  arms,  or  cirri,  now  bud  out  as  two  prominences,  one  on 
each  side  of  the  mouth.  Then  as  the  embryo  advances  in 
growth  the  outlines  remind  one  of  a  Leptcena,  an  ancient 
genus  of  Brachiopods,  and  in  a  later  stage  the  form  becomes 
quite  unlike  any  adult  Brachiopod  known. 

The  deciduous  bristles  are  then  discarded,  and  the  perma- 
nent ones  make  their  appearance,  two  pairs  of  arms  arise, 
and  now  the  shell  in  "its  general  contour  recalls  Siphono- 
treta,  placed  in  the  family  Discinidce  by  Davidson,  a  genus 
not  occurring  above  the  Silurian."  No  eye-spots  could  be 
seen  in  Tercbratulina,  though  in  the  young  Thecidium  they 
were  observed  by  Lacaze-Duthiers.  The  young  Terebratu- 
lina  differs  from  Discina  of  the  same  age  in  being  sedentary, 
while,  as  observed  by  Fritz  Miiller,  the  latter  "swims  freely 
in  the  water  some  time  after  the  dorsal  and  ventral  plates, 
cirri,  mouth,  oesophagus  and  stomach  have  made  their  ap- 
pearance." Discina  also  differs  from  Terebratulma  in  hav- 
ing a  long  and  extensible  oesophagus  and  head  bearing  a 
crown  of  eight  cirri  or  tentacles.  Regarding  the  relations 
of  the  Bracliiopods  with  the  Polyzoa,  Morse  suggests  that 
there  is  some  likeness  between  the  young  Brachiopod  and 
the  free  larva  of  Pedicellina.  Fig.  133,  B,  represents  the 
Terebratulina  when  in  its  form  it  recalls  Megerlia  or  Argi- 
ope.  0  represents  a  later  Lingula-like  stage.  "It  also 
suggests,"  says  Morse,  "in  its  movements,  the  nervously 
acting  Pedicellina.  In  this  and  the  several  succeeding 
stages,  the  mouth  points  directly  backward  (forward  of 


194  ZOOLOGY. 

authors),  or  away  from  the  perpendicular  end  (D),  and  is 
surrounded  by  a  few  ciliated  cirri,,  which  forcibly  recall  cer- 
tain Polyzoa.  The  stomach  and  intestine  form  a  simple 
chamber,,  alternating  in  their  contractions  and  forcing  the 
particles  of  food  from  one  portion  to  the  other."  Figure 
133,  E,  shows  a  more  advanced  stage,  in  which  a  fold  is 
seen  on  each  side  of  the  stomach  ;  from  the  fold  is  developed 
the  complicated  liver  of  the  adult,  as  seen  in  E,  which 
represents  the  animal  about  an  eighth  of  an  inch  long.  The 
arms  (lophophore)  begin  to  assume  the  horseshoe-shaped 
form  of  Pedinatella  and  other  fresh-water  Polyzoa.  At  this 
stage  the  mouth  begins  to  turn  towards  the  dorsal  valve,  and 
as  the  central  lobes  of  the  lophophore  begin  to  develop,  the 
lateral  arms  are  deflected  as  in  F.  In  the  stage  G  an  epis- 
tome  is  marked,  and  Morse  noticed  that  the  end  of  the 


G 


Fig.  133.— Later  larval  stages  of  Terebratulina.— After  Morse. 

intestine  was  held  to  the  mantle  by  an  attachment,  as  in  the 
adult,  reminding  one  of  the  funiculus  in  the  fresh-water 
Polyzoa.  In  tracing  the  development  of  Argiope,  Kowal- 
evsky  has  shown  that  the  larva  is  strikingly  like  those  of  the 
Annelids,  as  well  as  the  Tornaria  stage  of  Balanoglossus. 

While  in  their  development  the  Bracliiopoda  recall  the 
larva?  of  the  true  worms,  they  resemble  the  adult  worms  in 
the  general  arrangement  of  the  arms  and  viscera,  though 
they  lack  the  highly  developed  nervous  system  of  the  Anne- 
lids, as  well  as  a  vascular  system,  while  the  body  is  not 
jointed.  On  the  other  hand  they  are  closely  related  to  the 
Polyzoa,  and  it  seems  probable  that  the  Brachiopods  and 
Polyzoa  were  derived  from  common  low  vermian  ancestors, 
while  the  true  Annelids  probably  sprang  independently 
from  a  higher  ancestry.  They  are  also  a  generalized  type, 


DISTRIBUTION  OF  BRACH10PODS.  195 

having  some  molluscan  features,  such  as  a  solid  shell,  though 
having  nothing  homologous  with  the  foot,  the  shell-gland 
or  odontophore  of  mollusks. 

In  accordance  with  the  fact  that  the  Brachiopods  are  a 
generalized  type  of  worms,  the  species  have  a  high  antiquity, 
and  the  type  is  remarkably  persistent.  The  Lingula  of  our 
shores  (L.  pyramidata  Stimpson,  Fig.  134)  lives  buried  in 
the  sand,  where  it  forms  tubes  of  sand  around  the  peduncle, 
just  below  low- 
water  mark  from 
Chesapeake  Bay, 
to  Florida.  It  has 
remarkable  vital- 
ity,  not  only  with- 
standing  the 
changes  of  tem- 
perature and  ex- 
posure to  death 

from  Various  otll-        Fig.    134.— Lingula  pyramidata  making  sand-tubes ; 
,     natural  size.— After  Morse. 

er  causes,  but  will 

bear  transportation  to  other  countries  in  sea- water  that  has 
been  unchanged.  Living  Lingulae  have  been  carried  by  Prof. 
Morse  from  Japan  to  Boston,  Mass.,  the  water  in  the  small 
glass  jar  containing  the  specimens  having  been  changed  but 
twice  in  four  months.  The  living  species  of  this  cosmopol- 
itan genus  diifer  but  slightly  from  those  occurring  in  the 
lowest  fossiliferous  strata.  Between  eighty  and  ninety  liv- 
ing species  are  known,  most  of  them  living,  except  Lingula, 
which  is  tropical,  in  the  temperate  or  arctic  seas,  while  nearly 
2000  fossil  species  are  known.  The  type  attained  its  maxi- 
mum in  the  Silurian  age,  and  in  palaeozoic  times  a  few  spe- 
cies, as  A  trypa  reticularis,  extended  through  an  entire  system 
of  rocks  and  inhabited  the  seas  of  both  hemispheres. 


CLASS  V.— BRACHIOPODA. 

Shelled  worms,  with  a  limestone  or  partly  chitlnous,  inequivalve,  hinged 
or  unhinged  shell,  enclosing  the  worm-like  animal ;  with  two  spirally  coiled 
arms  provided  with  dense  ciliated  cirri  or  tentacles,  and  capable  of  reaching 


196  ZOOLOGY. 

to  or  beyond  tlie  edge  of  the  gaping  shells  ;  alimentary  canal  with  the  mouth 
opening  between  the  arms,  an  oesophagus,  stomach  with  a  licer-mass  on 
each  side,  and  a  short  intestine  ending  in  a  blind  sac,  and  with  the  stomach 
freely  suspended  in  the  perivisceral  space-.  Nervous  system  consisting  of  a 
ganglion  above  and  beneath  the  oesophagus,  and  two  lateral  ventral  icidely- 
separated  threads.  No  eyes  in  the  adult,  but  present  in  tlie  larvcv  of 
Argiope  and  Thecidium  ;  auditory  sacs  present  in  Lingula.  No  circulatory 
system,  the  blood  impelled  through  the  visceral  interspaces  and  tentacular 
sinuses  by  ciliary  action  alone.  Respiration  carried  on  mainly  in  the 
mantle  and  also  in  the  arms.  The  sexes  distinct.  One  or  two  pairs  of  seg  • 
mental  organs.  The  germ  passes  through  a  morula  and  gastrula  stage, 
becoming  a  segmented  ciliated  larva  like  that  of  the  true  worms,  which  be- 
comes sessile,  the  shell  developing  from  the  thoracic  segment  of  the  larva  and 
gradually  enclosing  the  animal. 

Order  1.  Testicardines. — Shell  calcareous,  of  prismatic  structure,  with 
hinge  and  teeth.  Intestine  ending  in  a  blind  sac.  Mantlo 
lobes  united  behind.  (Families  Terebratulidae,  Spirifcridae, 
Rhynchonellidae,  Strophomenida3,  and  Productida?.) 

Order  2.  Ecardines. — Shell  without  a  hinge  ;  arms  without  a  calcare- 
ous loop  and  with  no  median  lobe.  Intestine  either  end- 
ing in  a  blind  sac  or  with  a  vent  opening  anteriorly  on  the 
right  side.  (Families  Craniidse,  Discinidae,  and  Lingulidge.) 

Laboratory  Work. — Specimens  of  Terebratulina  can  be  dredged  in 
from  ten  to  fifty  fathoms  on  a  rocky  bottom  north  of  Cape  Cod,  and  the 
anatomy  and  development  of  the  young  be  studied  in  living  examples. 
Lingulae  can  be  obtained  at  Beaufort,  N".  C. ,  and  in  the  sandy  shores 
southward.  While  the  general  structure  can  be  studied  from  alcoholic 
specimens,  the  recent  discoveries  which  have  advanced  our  knowledge 
of  the  Brachiopods  have  been  made  on  living,  active  individuals.  The 
eggs  are  minute  and  have  to  be  studied  with  high  powers  of  the  micro- 
scope. 


CLASS  VI. — TUNIC  AT  A  (Ascidians,  Sea-squirts). 

General  Characters  of  Tunicates. — While  the  Tunicates 
are  an  aberrant  type  of  worms,  with  affinities  on  the  one 
hand  to  the  larvae  of  the  lower  worms,  -i.e.,  the  Ccrcaria 
form  of  the  Trematodes,  on  the  other  hand  they  have  a 
startling  resemblance  in  the  tadpole-like  young  of  many 
genera  to  the  vertebrate  Amphioxun.  The  position  given  to 
them  between  the  Brachiopods  and  true  worms  not  far  from 


HABITS  OF  ASCIDIANS.  197 

Balanoglossus,  is  a  provisional  one.  In  a  diagram  showing 
the  classification,  i.e.,  the  affinities  of  the  different  classes  of 
animals,  the  Tunicates  may  be  represented  as  an  independent 
branch  sent  off  possibly  from  the  Trematode  stem,  running 
parallel  to  the  worms,  near  Balanoglossus,  and  ending  a  little 
below  the  level  of  Ampliioxus.  They  have  certainly  few 
molluscan.  features,  what  do  exist  being  superficial,  and 
nothing  to  remind  us  closely  of  the  Polyzoa  or  Brachiopods, 
and  the  class  is  here  treated  of  because,  in  a  serial  arrange- 
ment of  the  classes  of  animals,  the  Tunicates  can  best  be 
described  at  this  place,  rather  than  after  the  true  worms,  or 
immediately  before  the  vertebrates. 

The  Ascidians  are  common  just  below  low-water  mark, 
cither  hidden  in  masses  of  mussels,  attached  to  the  rocks 
under  sea -weeds,  or  the  compound  species 
may  be  found  forming  bright-colored  masses 
on  the  piles  of  wharves  and  bridges,  while 
the  Botryllus  grows  on  the  leaves  of  eel- 
grass.  For  purposes  of  study  the  larger 
forms,  such  as  Ascidia,  Cynthia,  and  Bol- 
tenia,  may  be  dredged.  On  placing  a  good- 
sized  Ascidian  in  a  vessel  of  fresh  sea-water, 
it  will  be  found  to  consist  of  a  semi-trans- 
parent or  quite  opaque  test  with  two  open- 
ings,  one  lower  than  the  other,  as  seen  in 
Molgula,  which  looks,  when  the  two  orifices 
are  protruded,  like  a  double-necked  bottle.  The  anterior  or 
higher  orifice  or  mouth  is  for  the  passage  of  currents  of  water 
into  the  respiratory  sac,  and  the  posterior,  usually  lower, 
excurrent  orifice  for  the  passage  outwards  of  faecal  matter. 
The  test  is  either  delicate  and  semi-transparent,  allowing  the 
intestine  and  ovaries  and  liver  to  be  detected,  or  it  may  be 
quite  tough  and  opaque.  It  is  rendered  tough  and  hard  by 
the  presence  of  cellulose,  a  substance  usually  occurring  in 
the  walls  of  vegetable  cells,  but  very  rarely  in  animal  tis- 
sues. 

Order  1.  Ascidiacea. — As  an  example  of  the  ordinary  Tuni- 
cates, we  will  now  study  the  internal  anatomy  of  Boltenia 
reniformis  (Fig.  136),  which  lives  in  from  five  to  twenty-five 


198  ZOOLOGY. 

fathoms  off  the  coast  of  Northern  New  England,  but  which 
is  sometimes  thrown  ashore  on  beaches. 

On  examining  the  test  of  this  Ascidian,  which  is  mounted 
on  a  long  stalk,  the  oral  or  incurrent  orifice  is  seen  at  the 
insertion  of  the  stalk,  and  the  atrial  or  excurrent  orifice  on 
the  same  side  near  the  opposite  end.  On  cutting  open  the 
thick  test  and  throwing  the  flap  over  to  the  left,  the  deli- 
cate mantle  or  tunic  is  disclosed  ;  it  extends  a  short  distance 
into  the  stalk  or  peduncle.  This  thin  hyaline  mantle  is 
crossed  by  two  sets  of  narrow  raised  muscular  bands  ;  the 
transverse  fibres  arc  arranged  concentrically  to  the  two  ori- 
fices, so  as  to  close  or  open  them,  the  longitudinal  ones  curv- 
ing outward  from  the  left  side. 

Currents  "of  sea-water  laden  with  organic  food  pass  into 
the  oral  orifice,  which  is  surrounded  by  a  circle  of  tentacles 
pointing  inward,  and  thence  into  a  capacious  saccular  bran- 
chial chamber  within  the  mantle,  which  contracts  at  the 
bottom,  where  the  cesophageal  opening  is  situated.  The 
walls  of  this  chamber,  which  is  over  an  inch  long  in  a  good- 
sized  specimen,  and  gathered  into  fringed  folds,  is  sieve-like 
with  ciliated  perforations  (compare  Fig.  137  e),  making  the 
walls  like  a  lattice-work,  the  blood  coursing  through  the  ves- 
sels passing  between  the  meshes  of  the  sieve-like  walls. 

The  oesophagus,  which  lies  at  the  bottom  of  this  branchial 
chamber,  is  also  situated  near  the  intestine  passing  over 
the  anal  end  into  the  short  stomach.  The  intestine  is  long, 
passing  up  to  the  insertion  of  the  stalk,  where  it  is  held 
in  place  by  muscular  threads  extending  into  the  stalk  and 
attached  to  the  mantle  ;  it  then  suddenly  bends  back  and 
passes  straight  down  to  the  vent,  which  opens  opposite  to 
the  atrial  orifice  ;  the  end  of  the  intestine  is  in  part  revolute 
and  provided  with  a  fringe  of  about  twenty  filaments.  The 
liver  forms  a  broad  and  flat  mass  of  a  bright  livid  green,  and 
consists  of  three  flat  lobes  each  composed  of  eight  or  nine 
lobules,  with  very  short  ducts  enveloping  the  inner  aspect  of 
the  intestine.  The  ovaries  are  two  yellowish,  large  and  long 
lobulated  masses  extending  nearly  the  whole  length  of  the 
body,  while  the  right  one  is  a  little  smaller,  and  situated  in 
the  fold  of  the  intestine.  The  atrium  is  that  region  of  the 


STRUCTURE  OF  APPENDICULARIA.  199 

body-cavity  which  lies  hetween  the  end  of  the  intestine  and 
the  atrial  or  excurrent  orifice  ;  into  this  atrial  region  tho 
faeces,  eggs,  etc.,  pass  on  their  way  to  and  out  of  the  atrial 
orifice. 

The  simplest  form  of  Tunicate  is  Appendicularia,  which 
is  tadpole-shaped,  bearing  a  general  resemblance  to  the  larva 
of  an  ordinary  Ascidian,  so  that  it  may  be  properly  called  a 
larval  form.  The  Appendicularia  is  a  pelagic  animal,  usually 
about  a  quarter  of  an  inch  in  length,  found  floating  at  or 
near  the  surface  when  the  ocean  is  calm,  and  occurring  in 
all  seas  a  few  miles  from  land  or  in  mid-ocean.  It  swims 
by  means  of  its  large,  long,  broad,  flat  tail,  the  body  being- 


Fig.  136.— Anatomy  of  Boltenia.— Drawn  by  J.  S.  Kingsley  from  the  author's 
dissections. 

oval  or  flask-shaped.  In  Appendicularia  flabellum,  as  de- 
scribed by  Huxley,  the  caudal  appendage  is  three  or  four 
times  as  long  as  the  body.  The  mouth  leads  into  a  large 
pharyngeal  or  branchial  sac  ;  a  narrow  oesophagus  at  the 
bottom  of  this  sac  leads  to  a  spacious  stomach,  with  two 
lobes,  from  the  left  one  of  which  the  intestine  arises,  curves 
and  ends  midway  between  the  mouth  and  insertion  of  the 
tail.  In  the  middle  of  the  haemal  side  (that  side  in  which 
the  heart  is  situated  and  bearing  the  atrial  opening)  is  a 
fold  of  the  wall  of  the  pharyngeal  cavity  called  the  endostyle. 
On  each  side  of  this  endostyle  are  two  oval  ciliated  apertures, 


200 


ZOOLOGY. 


corresponding  to  the  numerous  branchial  slits  in  the  other 
^  Ascidians,  but  in  Appendicularia  each  oral 

^£5i/V  aperture  leads  into  a  funnel-shaped  atrial 
canal,  the  open  end  of  which  terminates 
beside  the  rectum. 

The  heart  is  a  large  pulsatile  sac  situated 
between  the  two  lobes  of  the  stomach.  The 
nervous  system  is  much  more  fully  developed 
than  in  other  Tunicates,  and  is  constructed 
on  the  true  Vermian  type,  consisting  first  of 
a  ganglion  situated  below  the  mouth  on  the 
side  opposite  the  atrial  opening  and  opposite 
the  anterior  end  of  the  endostyle.  This 
nerve-centre  throws  off  nerves  to  the  sides  of 
the  mouth,  and  from  it  posteriorly  extends  a 
long  cord  past  the  oesophagus  to  the  base  of 
the  tail,  thence  it  extends  along  one  side  of 
the  axis  of  the  tail  (urochord),  swelling  at 
regular  intervals  into  small  ganglia,  from 
which  from  two  to  five  small  nerves  radiate. 
On  the  cephalic  ganglion  a  round  ear-vesicle 
is  attached.  Behind  the  posterior  turn  of 
the  digestive  canal  is  the  testis  and  ovary, 
the  Appendicularia  being  hermaphrodite,  as 
Fol  claims,  though  the  ovary  is  developed 
later  than  the  testis.  The  Appendicularia 
has  no  test,  but  secretes  a  fibrous  envelope, 
which  is  at  first  gelatinous,  loosely  surround- 
Fig.  137.  —  struc-  ing  the  whole  body,  and  allowing  the  creature 

tnre  of  a  compound    ,,       „          ,  .  .  ,  .      .,  ., 

Ascidian,     Amarce-    the  freest  motion  Wltlllll  its  Cavity. 

The  general  structure  of  an  Ascidian  may 
perhaps  be  more  readily  comprehended  by  a 
study  of  a  compound  Ascidian  (Amar cerium), 
egg  in  the  body-cay-  which  grows  in  white  or  flesh-colored  masses 

ity;  p  ,  eggs  in  the  ° 

on  sea-weeds,  etc.  On  removing  an  Ama- 
rcecium  from  the  mass  and  placing  it  under 
the  microscope,  its  structure  can  be  per- 
ceived. The  body  is  long  and  slender,  as 
seen  in  Fig.  137.  The  mouth  leads  by  the  capacious  bran- 


ovarh-e 


'j :   .f  i  "i 

atrium  ;  n,  anus  ;  0, 
shows  the  site  of  the 
heart ;  /,  liver  ;  e, 
openings  in  wal;sof 
branchial  chamber. 
—From  Macalis  er. 


STRUCTURE  OF  ASCIDIANS.  201 

chial  sac  (A)  to  the  stomach,  while  the  intestine  (B)  is  flexed, 
directed  upwards,  ending  at  the  bottom  of  the  atrium  not 
far  from  the  atrial  opening.  The  reproductive  glands  are 
situated  behind  or  below  the  bend  of  the  intestine,  the  eggs 
being  fertilized  as  they  pass  into  tho  atrium,  and  the  heart 
lies  in  the  bottom  of  the  body-cavity,  being  directly  opposed 
to  the  nerve-ganglion  (not  represented  in  the  figure),  which 
lies  between  the  two  openings. 

In  the  perfectly  transparent  Peropliora,  which  grows  on 
the  piles  of  wharves  on  the  coast  of  Southern  New  England, 
one  individual  after  another  buds  out  (as  also  in  Clavellina) 
from  a  common  creeping  stalk  like  a  stolon.  In  this  form 
the  circulation  of  the  blood-disks  in  the  branchial  vessels  and 
the  action  of  the  heart  can  be  studied  by  placing  living  ani- 
mals in  glasses  under  the  microscope.  The  heart  is  a  straight 
tube,  open  at  each  end,  and  situated  close  to  the  hinder  end 
of  the  branchial  sac.  After  beating  for  a  number  of  times, 
throwing  the  blood  with  its  corpuscles  in  one  direction,  tho 
beatings  or  contractions  are  regularly  reversed  and  the  blood 
forced  in  an  opposite  direction. 

Eenal  organs  are  apparently  represented  in  Phallusia  by 
a  peculiar  tissue,  consisting  of  innumerable  spherical  sacs 
containing  a  yellow  concretionary  matter.  In  Molgula  and 
Ascidia  vitrea  Van  Beneden,  an  oval  sac  containing  concre- 
tions of  uric  acid  lies  close  to  tho  ovary. 

In  the  forms  already  considered  the  plan  of  structure  is 
complicated,  owing  to  the  difficulty  of  distinguishing  an 
anterior  or  posterior,  a  dorsal  or  ventral  aspect  of  the 
animal.  In  Salpa  and  DoUolum,  however,  the  body  is  more 
or  less  barrel-shaped,  the  hoops  of  the  barrel  represented  by 
the  muscular  bands  which,  at  regular  intervals,  surround  the 
body.  The  month  is  near  the  centre  of  the  front  end,  the 
pharyngeal  sac  is  very  large,  and  the  digestive  tract  makes 
less  of  a  turn  than  in  the  ordinary  Ascidians,  while  the 
atrial  opening  lies  directly  at  the  posterior  opening.  The 
heart  is  truly  a  dorsal  vessel,  and  the  nervous  ganglion  is 
situated  on  the  opposite  side  of  the  body.  This  relation  of 
the  anatomical  systems  is  most  clearly  shown  in  the  genus 
DoUolum,  and  we  have  here  a  slight  approach  to  the  sym- 


202  ZOOLOGY 

metrical  relation  of  parts  seen  in  the  true  worms,  and  which 
strongly  suggest  tho  conclusion  that  the  Tunicates  are  mod- 
ified worms,  This  conclusion  is  strengthened  by  the  fact 
that  in  Appendicularia  tho  ventral  nervous  cord  is  gangli- 
onated  at  intervals,  as  in  the  Annelids,  while  the  twisted 
digestive  tract  is  much  as  seen  in  Polyzoa  and  Brachiopods. 
Furthermore,  the  branchial  sac  is  strongly  analogous  to  tho 
pharyngeal  or  gill-sac  of  Bctlanoglossus,  and  this  structure  in 
the  Ascidian  and  whale's-tongue  worm  anticipates  the  pha- 
ryngeal or  gill-sac  of  Amphioxus  and  vertebrate  embryos. 

The  simple  Ascidians  attain  to  a  largo  size,  Ascidia  calloxa 
being  about  ten  centimetres  in  diameter,  quite  round,  and  in 
form  and  color  bears  a  strong  resemblance  to  a  potato. 
Ascidia  giyas,  dredged  by  the  Challenger  Expedition,  is  from 
thirty  to  forty  centimetres  in  diameter,  and  has  a  ganglion 
nearly  as  large  as  a  pea.  A  floating  colony  of  Pyrosoma, 
yigas  is  sometimes  five  feet  long.  Cynthia  pyriformis  Rathko 
may  be  called  the  sea-peach,  from  its  size,  form,  and  the  rich 
bloom  and  reddish  tints  of  its  test.  It  is  common  in  deep 
water  from  Cape  Cod  to  Greenland  and  Scandinavia. 

While  the  Ascidians  as  a  rule  do  not  live  below  a  depth  of 
150  fathoms,  the  stalked  Hypobythius  call/codes  Moseley  was 
dredged  by  the  Challenger  Expedition  in  2900  fathoms  in 
the  North  Pacific  Ocean ;  it  is  stalked,  and  about  twenty 
inches  high.  The  aberrant  Octacnemus  bythius  Moseley  was 
also  dredged  in  1070  fathoms  near  the  Schouten  Islands, 
Tasmania. 

Panceri  has  described  the  luminous  organs  of  Pyrosoma, 
which  is  highly  phosphorescent ;  the  substance  from  which 
the  light  is  emitted  is  probably  a  fatty  matter. 

Ascidians  multiply  by  budding  and  by  eggs.  Examples  of 
budding  or  germination  are  seen  in  the  compound  or  social 
Ascidians,  such  us  Amarwcium,  etc.,  where  the  individuals  of 
tho  colony  bud  out  from  the  primitive  one  just  as  it  has  left 
the  larval  condition  and  has  become  fixed.  In  Didemnium 
buds  arise  from  masses  of  cells  floating  free  within  the  test. 
They  multiply  by  division  as  soon  as  the  digestive  and  repro- 
ductive organs  are  indicated.  In  Botryllus  the  zooid  which 
results  from  the  tadpole -like  larva  serves,  according  to 


DEVELOPMENT  OF  ASCIDIANS.  203 

Huxley,  merely  as  a  kind  of  stalk,  from  which  new  zooids 
bud  out,  and  this  process,  in  his  opinion,  "leads  to  the  still 
more  singular  process  of  development  in  Pyrosoma,  in  which 
the  first  formed  embryo  attains  only  an  imperfect  develop- 
ment, and  disappears  after  having  given  rise  to  four  ascidio- 
zooids."  In  Clavellina  and  Perophora  the  original  parent 
Ascidian  throws  off  branches  or  stolons  from  which  develop 
new  individuals. 

The  usual  mode  of  development  in  the  simple  and  com- 
pound Ascidians  (forming  the  order  Ascidiacea)  is  by  fertil- 
ized eggs.  We  will  give  the  life-history  of  an  Ascidian  as 
based  on  Kowalevsky  and  Kupffer's  researches  on  Phallusia 
mammillata  Cuvier,  in  which  the  embryonic  stages  were  ob- 


a, 


Fig.  138.— Embryo  Ascidian.  A,  a,  primitive  opening ;  h,  primitive  digestive  cav- 
ity ;  6-,  segmentation-cavity  or  primitive  body-cavity  ;  B,  i,  pharynx  ;  n,  nerve-cavity; 
£,  epithelium  forming  the  body-wall ;  x,  rudimentary  notocnord.— After  Kowaleveky. 

served,  and  Ascidia  intestinalis,  in  which  the  larval  and 
subsequent  stages  were  studied. 

The  egg  consists  of  a  yolk  unprotected  by  a  yolk-skin,  but 
surrounded  by  a  layer  of  jelly  containing  yellow  cells.  The 
yolk  undergoes  total  segmentation.  The  next  step  is  the 
invagination  of  the  ectoderm,  a  true  gastrula  state  resulting. 
Fig.  138,  A  (after  Kowalevsky),  represents  the  gastrula ;  h, 
the  primitive  digestive  cavity ;  a,  the  primitive  opening, 
which  soon  closes  ;  and  c,  the  segmentation-cavity  or  primi- 
tive body-cavity.  After  this  primitive  opening  (a)  is  lost  to 
view,  sometime  before  the  embryo  has  reached  the  stage  B, 
another  cavity  (n)  appears  with  an  external  opening.  This 
cavity  is  formed  by  a  union  of  two  ridges  which  grow  out 


204  ZOOLOGY. 

from  the  upper  part  of  the  germ.  This  is  the  central  ner- 
vous system,  and  in  the  cavity  are  subsequently  developed 
the  sense  organs.  We  thus  see,  says  Kowalevsky,  a  com- 
plete analogy  in  the  mode  of  origin  of  the  nervous  system  of 
the  Ascidians  to  that  of  the  vertebrates,  the  nervous  cavity, 
where  the  embryo  is  seen  in  section,  being  situated  above 
the  digestive  cavity  in  both  types  of  animals. 

The  next  important  stage  is  the  formation  of  the  tail. 
The  pear-shaped  germ  elongates  and  contracts  posteriorly 
until  of  the  form  indicated  at  Fig.  138,  B.  At  this  period 
appears  the  axial  string  of  nucleated  cells,  called  the  chorda 
dor  salts,  as  it  is  homologous  with  that  organ  in  Ampldoxus 
and  the  embryo  of  higher  vertebrates.  The  nervous  system 
consists  of  a  mass  of  cells  extending  halfway  into  the  tail 
and  directly  overlying  the  chorda,  but  extending  far  beyond 
the  end  of  the  latter  as  seen  in  the  figure.  The  nerve-cav- 
ity (B,  n)  after  closing  up  forms  the  nerve-vesicle,  a  largo 
cavity  (Fig.  139,  a),  in  which  the  supposed  auditory  organ 
(e)  and  the  supposed  eye  (a)  arise  ;  this  cavity  finally  closes, 
and  the  sense-organs  are  indicated  by  certain  small  masses 
of  pigment  cells  in  the  fully  grown  Ascidian  larva. 

As  the  embryo  matures,  the  first  change  observed  in  the 
cord  is  the  appearance  of  small,  refractive  bodies  between 
the  cells.  Between  the  neighboring  cells  soon  appear  in  the 
middle  minute  highly  refractive  corpuscles  which  increase 
in  size,  and  press  the  cell-contents  out  of  the  middle  of  the 
cord.  After  each  reproductive  corpuscle  grows  so  that  the 
central  substance  of  the  cell  is  forced  out,  it  unites  with 
the  others,  and  then  arises  in  the  middle  of  the  simple  cel- 
lular cord  a  string  of  bodies  of  a  firm  gelatinous  substance 
which  forms  the  support  of  the  tail,  After  this  coalescence 
the  substance  develops  farther  and  presses  out  the  proto- 
plasm of  the  cells  entirely  to  the  periphery.  The  cord  when 
complete  consists  of  a  firm  gelatinous  substance  surrounded 
by  a  cellular  sheath  which  is  formed  of  the  remains  of  the 
cells  originally  comprising  the  rudimentary  cord.  The  cells 
lying  under  the  epithelial  layer  form  a  muscular  sheath  of 
which  the  cord  (Fig.  138,  c)  is  the  support  or  skeleton. 

The  alimentary  cavity  arises  from  the  primitive  cavity 


DEVELOPMENT  OF  ASCIDIANS. 


205 


(Fig.  138,  A,  li)  ;  whether  the  primitive  opening  (Fig.  138, 
A,  a]  is  closed  or  not,  Kowalevsky  says  is  an  interesting 
question.  According  to  analogy  with  many  other  animals 
it  probably  closes. 

The  larva  hatches  in  from 
forty-eight  to  sixty  hours  af- 
ter the  beginning  of  segmen- 
tation, and  is  then  of  the 
form  indicated  by  Fig.  139 
(copied  with  some  additions 
and  omissions  from  Kupffer's 
figure,  being  partly  diagram- 
matic). This  anatomist  dis- 
covered in  the  larva  of  As- 
cidia  canina,  which  is  more 
transparent  than  Kowalev- 
sky's  Phallusia  larva,  not 
only  a  central  nervous  cord 
overlying  the  chorda  dorsalis 
and  extending  well  into  the 
tail,  while  in  the  body  of  the 
larva  it  becomes  broader, 
club-shaped,  and  surrounds 
the  sensitive  cavity  (a\  but 
he  also  detected  three  pairs 
of  spinal  nerves  (s)  arising  at 
regular  intervals  from  the 
spinal  cord  (h,  lir)  and  dis- 
tributed to  the  muscles  (not 
represented  in  the  figure)  of 
the  tail  ;  KupfFer  calls  /  the 
middle  and  g  the  lower  brain- 

o-MTio-lirm         T>io  Whom/riv  Ch\ 
gangllOll.       me  pliarynx  (O), 

nr    rp«nirafr>rv      «PP      i«     nnw 
lespiratory     Sac,     IS     nOW 

VPrv     larcrp  •     if     rmpn<j     nr>«j 
Vtry     large  ,      It      OpCl    ,      pOS- 

tei'iorly  into  the  Stomach  and 
•  . 

intestine   (i)  ;    x    represents 

one  of  the  three  appendages  by  which  the  larva  fastens 

itself  to  some  object  when  about  to  change  into  the  adult, 


139.—  Larval  Ascidian.    a,    sense 
ontaining  the  eye;  ft, 
respiratory  sac  ;  c,  notochord  ;  e,  supposed 
J 


cavity  containing  the  eye;  ft,  pharynx  or 
otochord  ;  e,  supposed 
aiKitory  0rgan  .  f^  middle,  g,  lower  brain- 


^  ,    ,  - 

gang'i°n;  ^»  A,  spinal  cord;  s,  #,  a,  three 
*£?  Of  spinal  nerves  ;  j,  intestine  ;  t, 
body-wall,  consisting  of  epithelial  I  cells.- 
Copied  with  some  changes  from  Knpffer. 


206  ZOOLOGY. 

sessile  condition ;  t  indicates  the  body-wall,  consisting  of 
epithelial  cells. 

We  will  now,  from  the  facts  afforded  us  by  Kowalevsky, 
trace  the  changes  from  the  larval,  free-swimming  state  to 
the  sessile  adult  Ascidia,  which  may  be  observed  on  the 
New  England  coast  in  August.  After  the  larva  fastens  itself 
by  the  three  processes  to  some  object,  the  chorda  dorsalis 
breaks  and  bends,  the  cells  forming  the  sheath  surrounding 
the  broken  axial  cord.  The  muscular  fibres  degenerate  into 
round  cells  and  fill  the  space  between  the  chorda  and  the 
tegument,  the  jelly-like  substance  forming  a  series  of  wrin- 
kles. With  the  contraction  and  disappearance  of  the  tail  be- 
gins that  of  the  nerve-vesicle,  and  soon  no  cavity  is  left,  ^he 
three  processes  disappear  ;  the  pharynx  becomes  quadrangu- 
lar ;  and  the  stomach  and  intestine  are  developed,  being 
bent  under  the  intestine.  A  mass  of  cells  arises  on  the  an- 
terior end  beneath  the  digestive  tract,  from  which  originate 
the  heart  and  pericardium.  In  a  more  advanced  stage,  two 
gill-holes  appear  in  the  pharynx,  and  subsequently  two  more 
slits,  and  about  this  time  the  ovary  and  testis  appear  at  the 
bottom,  beyond  the  bend  of  the  alimentary  canal.  The  free 
cells  in  the  body-cavity  are  transformed  into  blood-cells,  and 
indeed  the  greater  part  of  those  which  composed  the  nervous 
system  of  the  larva  are  transformed  into  blood-corpuscles. 
Of  the  embryonal  nervous  system  there  remains  a  very  small 
ganglion,  no  new  one  being  formed.  The  adult  Ascidian 
form  meanwhile  has  been  attained,  and  the  very  small  indi- 
viduals differ  for  the  most  part  only  in  size  from  those  which 
are  full-sized  and  mature. 

It  will  be  seen  that  some  highly  important  features,  recall- 
ing vertebrate  characteristics,  have  occurred  at  different  pe- 
riods in  the  life  of  the  embryo  Ascidian.  Kowalevsky  remarks 
that  "  the  first  indication  of  the  germ,  the  direct  passage  of 
the  segmentation  cells  into  the  cells  of  the  embryo,  the  for- 
mation of  the  segmentation-cavity,  the  conversion  of  this 
cavity  into  the  body-cavity,  and  the  formation  of  the  diges- 
tive cavity  through  invagination — these  are  all  occurrences 
which  are  common  to  many  animals,  and  have  been  observed 
in  Amphioxus,  Saqitta,  PJioronis,  EcMnus,  etc.  The  first 


RELATION  OF  ASCIDIANS  TO  VERTEBRATES.     207 

point  of  difference  from  other  animals  in  the  development 
of  all  vertebrates  is  seen  in  the  formation  of  the  dorsal 
ridges,  and  their  closing  to  form  a  nerve-canal.  This  mode 
of  formation  of  the  nervous  system  is  characteristic  of  the 
vertebrates  alone,  except  the  Ascidians.  Another  primary 
character  allying  the  Ascidians  to  the  vertebrates,  is  the 
presence  of  a  chorda  dorsalis,  first  seen  in  the  adult  Appen- 
dicularia  by  J.  Miiller.  This  organ  is  regarded  by  Kowal- 
evsky  to  be  functionally,  as  well  as  genetically,  identical  with 
that  of  Amphioxus.  This  was  a  startling  conclusion,  and 
stimulated  Professor  Kupffer,  of  Kiel,  to  study  the  embry- 
ology of  the  Ascidians  anew.  He  did  so,  and  the  results  this 
careful  observer  obtained  led  him  to  fully  endorse  the  con- 
clusions reached  by  Kowalevsky,  particularly  those  regarding 
the  unexpected  relations  of  the  Ascidians  to  the  vertebrates, 
and  it  would  appear  from  the  facts  set  forth  by  these  emi- 
nent observers,  as  well  as  Metschnikoff,  G-anin,  Ussow,  and 
others,  that  the  vertebrates  have  probably  descended  from 
some  type  of  worm  resembling  larval  Ascidians  more  perhaps 
than  any  other  vermian  type,  though  it  is  to  be  remembered 
that  certain  tailed  larval  Distomee  appear  to  possess  an  organ 
resembling  a  chorda  dorsalis,  and  farther  investigation  on 
other  types  of  worms  may  lead  to  discoveries  throwing  more 
light  on  this  intricate  subject  of  the  ancestry  of  the  verte- 
brates. At  any  rate,  it  is  among  the  lower  worms,  if  any- 
where, that  we  are  to  look  for  the  ancestors  of  the  Vertebrates, 
as  the  Coelenterates,  Echinoderms,  the  Mollusks,  Crustacea 
and  Insects,  are  too  circumscribed  and  specialized  groups  to 
afford  any  but  characters  of  analogy  rather  than  affinity. 

For  example,  the  cuttlefish,  with  its  "  bone,"  brain-cap- 
sule and  highly-developed  eye,  is,  on  the  whole,  more  remote 
from  the  lowest  vertebrate,  Amphioxus,  than  the  Appendi- 
culariajor  the  larval  Ascidian. 

Certain  (three)  species  of  Molgula  have  been  found  by 
Lacaze-Duthiers  to  have  a  nearly  direct  development,  not 
producing  tailed  young.  There  is  a  slight  metamorphosis, 
however,  the  young  having  five  temporary,  long,  slender 
processes.  In  Ascidia  ampulloides  the  larva  has  a  tail,  no- 
tochord  and  pigment  spots,  which  are  wanting  in  the  young 


208 


ZOOLOGY. 


of  several  species  of  Molgula,  but  it  has  the  five  long  decid- 
uous appendages  observed  in  young  Molgulce.  Among  the 
compound  Ascidians,  Botryllus  and  Botrylloides  have  tailed 
young,  while  in  other  forms  there  is  no  metamorphosis,  de- 
velopment being  direct. 

Order  2.  Thaliacea. — On  the  whole,  we  may  regard  this 
order,  represented  by  Salpa  (Fig.  140),  and  Doliolum,  as 
comprising  the  more  specialized  forms  of  Tunicates.  Salpa 
is  pelagic,  one  species  occurring  in  abundance  off  the  shores 

of  Southern  New  England,  while 
the  others  mostly  live  on  the  high 
seas  all  over  the  tropical  and  sub- 
tropical regions  of  the  globe.  Late 
in  the  summer  our  Salpa  spinosa 
of  Otto  can  be  captured  in  multi- 
tudes by  the  tow-net  in  Long  Island 
Sound. 

There  are  in  Salpa  two  kinds  of 
individuals,  i.e.,  the  solitary,  and 
aggregated  or  chain-Salpse.  The 
body  of  the  solitary  or  asexual 
form  is  more  or  less  barrel-shaped, 
with  a  series  of  circular  bands  of 
muscles,  like  the  hoops  of  a  barrel, 
and  situated  on  the  inner  side  of 
the  outer  tunic.  The  test  is  trans- 
parent, though  very  thick,  while 
the  outer  tunic  lines  the  cavity  of 
the  test  as  in  other  Tunicates.  In 
the  members  of  this  order  the  oral 
Agassiz,  fromVer:  aperture  of  the  mantle  is  at  one 
end  of  the  body,  and  the  atrial 
opening  at  the  opposite  end,  the  minute  digestive  canal  be- 
ing but  slightly  curved,  the  body-cavity  being  largely  occu- 
pied by  the  pharyngeal  or  respiratory  sac.  Moreover,  the  dor- 
sal or  haemal  side  of  the  body  is  clearly  distinguishable  from 
the  ventral  or  neural  side,  as  well  seen  in  Doliolum,  where 
the  well-marked  tubular  heart  lies  above  the  digestive  organs, 
and  is  directly  opposed,  as  in  worms  generally,  to  the  nervous 


Fig.  140.— Salpa  spinosa.  An  in- 
dividual from  a  mature  chain  ; 
three-quarter  view,  enlarged,  a, 
atrial  opening  ;  b,  mouth  ;  c,  pro- 
cesses by  which  the  members  of 
the  chain  are  united  ;  h,  heart ;  n, 
nervous  ganglion  ;  0,  nucleus  ;  ?% 
gill.— After  A. 
rill's  Report. 


STRUCTURE  OF  8ALPA.  209 

system,  which  is  situated  ventrally  between  the  mouth  and 
vent.  We  thus  have  in  these  Tunicates  a  front  and  hind 
end  of  the  body,  a  dorsal  and  ventral,  as  well  as  a  distinct 
bilateral  symmetry  of  the  body.  This  is  seen  in  Appendi- 
cularia  as  well  as  in  Doliolum  and  Salpa,  however  much 
this  symmetry  may  be  obscured  in  the  more  typical  Ascidi- 
ans,  such  as  Ascidia,  Molgula,  Boltenia,  etc. 

The  oral  aperture  leading  into  the  respiratory  sac  is  large, 
being  as  wide  as  the  body  ;  the  respiratory  sac  is  more  com- 
plicated than  in  other  Ascidians,  and  more  so  than  in  Doli- 
olum, where  it  is  a  wide,  deep  passage,  the  oesophagus  at  the 
hinder  end,  the  sac  itself  perforated  by  two  rows  of  bran- 
chial slits,  four  or  five  slits  in  each  row.  In  Salpa,  how- 
ever, the  respiratory  sac,  as  described  by  Brooks,  is  attached 
to  the  outer  tunic,  around  the  edges  of  the  mouth,  as  in 
other  Tunicates.  There  are  only  two  branchial  slits,  one  on 
each  side  ;  these  are  very  large,  and  cover  almost  the  whole 
surface  of  the  branchial  sac,  except  the  median  dorsal  and 
haemal  lines.  On  the  neural  side  the  branchial  slit  opens 
directly  into  the  atrium,  the  ciliated  line  where  the  two 
tunics  unite  being  marked  by  the  so-called  "gill"  (Brooks). 
In  Salpa,  according  to  Brooks,  the  branchial  sac,  though 
ciliated  within,  is  not  so  directly  concerned  in  the  respiratory 
act  as  in  other  Tunicates,  since  respiration  is  effected  largely 
by  the  action  of  the  muscles,  which  also  assist  deglutition, 
and  are  the  organs  of  locomotion.  These  contract  rythmi- 
cally,  with  great  regularity,  and  at  each  contraction  the 
water  is  expelled  from  the  branchial  sac  through  the  atrial 
aperture  ;  and  when  the  muscles  are  relaxed,  the  elasticity 
of  the  test  distends  the  chamber,  and  a  fresh  supply  is  drawn 
in  through  the  branchial  aperture,  the  lips  of  which  readily 
admit  its  passage  in  this  direction,  while  a  similar  set  of 
valves  allows  its  passage  out  of  the  atrial  aperture,  but  pre- 
vents its  return."  Thus  a  chain  of  individuals  move  with  a 
uniform  motion,  while  the  solitary  individuals  and  those 
which  have  been  set  free  by  the  breaking  up  of  a  chain,  move 
by  jerks. 

The  digestive  canal  is  small,  curved  on  itself,  the  cesopha- 
gus  leading  from  the  bottom  of  the  pharyngeal  or  respiratory 


210  ZOOLOGY. 

sac  into  a  small  stomach,  the  intestine  bending  back  on 
itself,  and  the  vent  being  near  the  month.  The  entire  diges- 
tive canal  is  immovable,  the  food  being  driven  through  the 
permanently  distended  cavity  by  means  of  the  cilia  lining 
its  inner  surface.  The  great  posterior  blood-sinus  surrounds 
the  digestive  system  on  all  sides,  the  nutriment  being  di- 
rectly absorbed  from  its  surface  and  mixed  with  the  blood. 

The  nervous  system  is,  in  adaptation  to  its  locomotive  life, 
more  specialized  than  in  the  sessile  forms,  and  highly  spe- 
cialized organs  of  sight  and  hearing  arc  present.  The  heart 
is  a  short,  complicated  organ,  lying  in  the  sinus-system.  Its 
action  is  often  reversed ;  the  reversal  of  the  beats  tending 
to  clear  the  sinuses  of  the  blood-disks  overcrowding  them. 
In  one  species  of  Salpa  Prof.  Brooks  states  that  the  blood- 
channels  are  in  all  cases  sinuses,  which  are  parts  of  the  body- 
cavity  and  have  no  special  walls,  though  in  species  investi- 
gated by  other  writers  there  are  said  to  be  true  blood-vessels, 
lined  with  epithelium. 

The  hermaphroditic,  aggregated  or  chain-salpa  differs  from 
the  solitary  asexual  form  in  being  less  regularly  barrel- 
shaped,  and  without  the  two  long  posterior  appendages  of 
the  latter ;  in  the  proportions  of  the  different  organs,  the 
two  forms  are  essentially  alike. 

The  young  chain  is  easily  perceived  in  the  solitary  indi- 
viduals in  the  posterior  part  of  the  body,  curving  around  the 
digestive  organs.  When  first  set  free  from  the  body  of  the 
solitary  Salpa,  the  chain  is  about  half  an  inch  long,  and  the 
single,  individual  Salpae  composing  it  are  about  two  and  a  half 
millimetres  in  length.  They  grow  very  rapidly,  and  soon 
reach  their  f  'ill  size,  when  the  chains  are  often  a  foot  or  a 
foot  and  a  half  long  ;  the  individuals  composing  them  when 
fully  grown  being  about  two  centimetres  in  length.  The 
chain  easily  falls  apart,  and  the  individuals  are  capable  of 
living  a  solitary  life,  Huxley  stating  that  the  chain-individu- 
als of  the  species  observed  by  him  were  generally  found  soli- 
tary ;  for  this  reason  we  should  regard  the  chain-salpse  as 
individuals,  not  zooids,  being  capable  of  leading  an  inde- 
pendent existence,  and  with  a  structure  almost  identical  with 
that  of  the  solitary  Salpse. 


DEVELOPMENT  OF  SALPA.  211 

Brooks  has  studied  the  mode  of  development  of  the  female 
and  male  Salpa  spinosa  (Fig.  140).  When  a  Salpa-chain  is 
discharged  from  the  body  of  the  asexual  Salpa,  each  indi- 
vidual of  the  chain  contains  a  single  egg  which  is  fertilized 
by  sperm-cells  of  individuals  belonging  to  some  other  chain, 
and  after  passing  through  the  mulberry  stage  and  entering 
the  gastrula  stage,  the  germ  is  in  most  intimate  relation 
with  the  body  of  its  parent.  The  vase-shaped  gastrula  is 
lodged  in  a  brood-sac.  Its  body-cavity,  originally  formed  by 
invagination  of  the  "ectoderm,  opens  directly  into  the  sinus- 
Gystem  of  its  nurse,  and  the  blood  now  circulates  in  and  out 
of  the  primitive  digestive  cavity  as  well  as  around  the  out- 
side of  the  embryo.  But  as  the  embryo  grows  and  fills  the 
brood-sac,  so  that  the  outer  surface  of  the  gastrula  becomes 
intimately  connected  with  the  wall  of  the  brood-sac,  the 
blood  no  longer  bathes  the  outside  of  the  embryo. 

At  this  time  the  "placenta"  is  formed.  Brooks  believes 
that  it  originates  directly  from  the  blood,  "  by  the  aggrega- 
tion and  fusion  of  its  corpuscles,"  not  being  derived  from  any 
of  the  parts  of  the  parent  or  embryo.  Soon  after  its  appear- 
ance it  consists  of  an  inner  chamber  communicating  with  the 
sinus  of  the  nurse,  and  having  no  communication  with  any 
of  the  cavities  of  the  embryo  ;  its  cavity  being  a  part  of  the 
original  "primitive  stomach"  of  the  gastrula.  It  finally  has 
two  chambers,  an  inner  and  outer  one,  and  Huxley  describes* 
the  foetal  circulation  in  the  placenta,  a  deciduous  organ 
analogous  in  function,  but  by  no  means  homologous  in  struc- 
ture, with  the  vertebrate  placenta. 

When  the  embryo  of  the  solitary  Salpa  is  about  four 
millimetres  (-fa  inch)  long,  and  while  still  in  the  brood-sac  of 
the  parent,  the  tube  which  is  to  give  rise  to  the  chain  ap- 

*  "  The  blood-corpuscles  of  the  parent  may  be  readily  traced  enter, 
ing  the  inner  sac  on  one  side  of  the  partition,  coursing  round  it,  and 
finally  re-entering  the  parental  circulation  on  the  other  side  of  the  par- 
tition ;  while  the  foetal  blood-corpuscles,  of  a  different  size  from  those 
of  the  parent,  enter  the  outer  sac,  circulate  round  it  at  a  different  rate, 
and  leave  it  to  enter  into  -the  general  circulation  of  the  dorsal  sinus. 
More  obvious  still  does  the  independence  of  the  two  circulations  be- 
come when  the  circulation  of  either  mother  or  foetus  is  reversed/' 


212  ZOOLOGY. 

pears  within  its  body.  "We  will  now  briefly  trace  the  devel- 
opment of  the  chain-salpa,  condensing  Brooks's  statement. 
The  aforesaid  tube  is  at  first  simply  a  cup-like  protrusion  of 
the  outer  tunic  into  the  cellulose  test  which  now  surrounds 
the  embryo  ;  the  cavity  of  the  cup  is  an  offshoot  from  the 
sinus-system,  the  blood  passing  in  and  out  of  it.  A  small 
bud-like  protrusion  now  appears  upon  the  surface  of  the  per- 
icardium, and  lengthens  to  form  a  long  rod  or  stolon,  ex- 
tending across  the  sinus  and  projecting  into  the  cavity  of  the 
cup.  At  about  this  period  a  long,  club-shaped  mass  of  pro- 
toplasm appears  within  each  of  the  sinus-chambers  of  the 
tube,  and  soon  after  the  outer  wall  is  constricted  at  regular 
intervals,  each  segment  being  destined  to  form  the  outer  tu- 
nics of  the  chain-salpse,  the  constrictions  indicating  the 
bodies  of  the  latter. 

By  the  deepening  of  these  constrictions,  each  of  the 
sinus-chambers,  which  are  diverticula  from  the  body-cav- 
ity of  the  solitary  Salpa,  becomes  divided  up  to  form  the 
body-cavities  of  the  Salpae  on  one  side  of  the  chain.  From 
the  central  tube  of  the  stolon  arises  a  row  of  buds  on  each 
side,  which  become  the  branchial  and  digestive  organs  of  the 
Salpae  on  each  side  of  the  chain  ;  while  a  similar  double  row, 
upon  the  other  edge,  gives  rise  to  the  ganglia.  The  club- 
shaped  organs  within  the  sinus-chambers  become  divided  up 
into  single  rows  of  eggs,  one  of  which  passes  into  the  body- 
cavity  of  each  chain-salpa  at  a  very  early  period  of  develop- 
ment. 

Thus,  as  Huxley  states,  budding  occurs,  not  from  the  outer 
wall  alone,  as  in  Hydroids  and  Polyzoa,  "  but,  from  the  first, 
several  components,  derived  from  as  many  distinct  parts  of 
the  parental  organism,  are  distinguishable  in  it,  and  each  com- 
ponent is  the  source  of  certain  parts  of  the  new  being,  and 
of  these  only."  Prof.  Brooks  adds  that  while  these  changes 
are  going  on  the  constrictions  on  the  surface  deepen,  the 
wall  protruding  from  them,  and  each  is  soon  seen  to  mark 
off,  on  each  side  of  the  stolon,  the  body  of  a  young  Salpa, 
which  soon  becomes  visible  to  the  naked  eye.  They  do  not 
increase  in  size  gradually  from  one  end  of  the  stolon  or  tube 
to  the  other,  but  develop  in  sets  of  from  thirty  to  fifty  each, 


GENERATIONS  OF  SALPA.  213 

and  the  development  of  all  which  are  embraced  within  a  set 
progresses  uniformly ;  there  are  usually  three  of  these  sets 
upon  the  tube  of  an  adult  solitary  Salpa.* 

Thus  the  Salpa  reproduces  parthenogenetically  as  in  some 
Crustacea  and  insects,  and  we  have  here  a  true  case  of  ' '  alter- 
nation of  generations."  In  1819  Chamisso  stated  "that  a 
Salpa  mother  is  not  like  its  daughter  or  its  own  mother,  but 
resembles  its  sister,  its  granddaughter,  and  its  grandmother.! 

Immediately  after  the  publication  of  Brooks'  researches 
on  Salpa  spinosa,  those  of  Salensky  on  Salpa  democratica- 
mucronata  (a  species  said  to  be  closely  allied  if  not  identical 
with  S.  spinosa)  appeared.  According  to  the  Russian  ob- 
server, as  stated  by  Huxley,  who  adopts  his  conclusions,  the 
chain-salpa  is  a  hermaphrodite,  and  the  egg  while  still  in 
the  ovarian  follicle  is  fertilized,  Avhen  the  oviduct  shortening 
and  widening  forms  a  single  uterine  sac,  the  maternal  and 

*  The  Development  of  Salpa,  by  W.  K.  Brooks.  Bulletin  of  the 
Museum  of  Comparative  Zoology,  III.,  No.  14,  Cambridge,  1876.  We 
have  presented  quite  fully  the  author's  account  of  the  mode  of  devel- 
opment of  the  young  asexual  (his  female)  Salpa,  without,  however, 
adopting  his  interpretation  of  the  sexes  of  the  two  kinds  of  individuals 
of  Salpa  ;  believing  his  "  female"  Salpa  to  be  asexual,  and  his  "  male" 
Salpa  to  be  hermaphrodite,  with  an  ovary  and  testis,  as  he  has  not  ap- 
parently observed  the  fact  of  the  introduction  of  an  egg  into  the  body 
of  his  "male"  Salpa.  On  the  contrary,  it  appears  to  be  developed 
originally  in  a  true,  simple  ovary  or  "  ovarian  follicle ;"  the  testis  being 
immature  and  the  egg  fertilized  by  sperm-cells  of  other  hermaphro- 
dites, in-and-in  breeding  thus  being  prevented. 

f  This  view  has  been  endorsed  by  Steenstrup,  Sars,  Krohn,  and 
others,  especially  by  Leuckart  in  the  following  words  quoted  by 
Brooks:  "It  is  now  a  settled  fact  that  the  reproductive  organs  are 
found  only  in  the  aggregated  individuals  of  Salpa,  while  the  solitary 
individuals,  which  are  produced  from  the  fertilized  eggs,  have,  in 
place  of  sexual  organs,  a  bud-stolon,  and  reproduce  in  the  asexual 
manner  exclusively,  by  the  formation  of  buds.  Male  and  female 
organs  are,  so  far  as  we  yet  know,  united  in  the  Salpae  in  one  indi- 
vidual. The  SalpCB  are  liermaphrodite."  On  the  other  hand,  Todaro, 
in  an  elaborate  memoir  (1876),  considers  the  Salpa  as  the  synthetic 
type  of  all  the  vertebrata,  presenting  features  peculiar  to  each  class, 
even  including  the  mammals.  In  his  opinion  it  is  an  allantoidian  ver- 
tebrate, developed  in  a  true  uterus,  the  neck  of  which,  after  the  life  of 
the  embryo  begins,  becomes  plugged  with  mucus. 


214  ZOOLOGY. 

embryonic  parts  of  the  placenta  arising,  respectively,  from 
the  wall  of  the  ovarian  sac  and  from  certain  large  cells  (blas- 
tomeres)  on  the  adjacent  (hsemal)  face  of  the  embryo.  Thus 
the  asexual  development  of  the  Salpa  is  like  that  of  the  germ- 
masses  destined  to  form  the  Cercarice  developed  in  the  body 
of  the  Redia  of  the  Distoma ;  and  is  also  like  that  of  the 
plant  lice  (Huxley).  This  is  a  reaffirmation  and  extension 
of  the  original  view  of  Chamisso. 

To  recapitulate,  the  life-history  of  the  Salpa  is  as  follows  : 
There  are  two  kinds  of  individuals  :  «,  solitary,  asexual  ;  I, 
social,  aggregated,  and  hermaphroditic. 

(1.)  The  solitary,  asexual  Salpa  produces  by  budding  a 
chain  of  hermaphrodite  Salpaa ;  the  latter  produce  a  fertil- 
ized 

(2.)  Egg,  which  passes  through  a — 

(3. )  Morula  and — 

(4. )  Gastrula  stage,  contained  and  growing  in  a  placenta- 
like  organ,  where  the  embryo  is  directly  nourished  by  the 
blood  of  the  parent,  the  embryo  finally  becoming — 

(5.)  A  solitary  asexual  Salpa. 

We  thus  have  a  true  alternation  of  generations,  like  the 
sexless  Hydroid  and  its  sexual  Medusa,  the  asexual  Aphis 
and  its  last  brood  of  males  and  females ;  the  asexual  Redia 
and  the  sexual  Disloma  ;  in  all  these  cases  the  offspring  (t>) 
of  the  asexual  individual  (a)  is  unlike  the  parent,  but  the  off- 
spring (c)  of  the  second  generation  (#)  is  like  (a)  the  grand- 
parent. 

Lastly, while  some  true  worms  (e.g.,  Balanoglossus),  and  the 
mollusks  through  the  cuttle-fish,  present  strong  features  an- 
ticipating the  vertebrate  structure,  the  Tunicata  seem  more 
closely  allied  to  the  vertebrates,  particularly  Ampliioxus,  than 
any  other  invertebrate  type.  To  sum  up  these  resemblances  : 
the  larval  Ascidian  has  a  notochord,  a  spinal  nerve-cord, 
and  sets  of  spinal  nerves,  like  those  of  lowly  organized  or  em- 
bryonic vertebrates,  though  these  are  morphologically  on  the 
ventral  side  of  the  body,  as  in  other  worms  ;  the  nervous 
cavity  and  its  mode  of  closure  in  the  embryo  is  as  in  the  em- 
bryo vertebrate ;  the  respiratory  sac  of  the  adult  Tunicate 
resembles  morphologically  that  of  the  Aviphioxus.  Conse- 


CHARACTERISTICS  OF  TUN1CATES.  215 

quen'tly,  while  as  a  matter  of  fact  the  Tunicates,  as  a  whole, 
resemble,  and  as  it  were  anticipate,  the  advent  of  a  verte- 
brate, like  Amphioxus  ;  as  a  matter  of  pure  hypothesis,  the 
Vertebrates  may  have  descended  from  animals  like  Tunicates. 
But  we  need  not  on  this  account  dissociate  the  Tunicates  from 
the  worms,  remembering  their  resemblance  to  Balanoglos- 
sus,  and  even  to  the  Trematodes,  and  place  them  near  Am- 
phioxus and  the  Vertebrates  in  general.  But  we  are  obliged 
to  leave  them  at  this  point  and  pass  on  to  the  consideration 
of  the  highly  specialized  worms  and  Mollusca.  Crustacea,  and 
Insecta,  which  are  circumscribed,  closed  types  of  animals 
with  possibly  a  vermian  ancestry. 


CLASS  VI.— TUNICATA. 

Body  usually  subsphcrical,  or  sac-like,  obscurely  symmetrical ;  some* 
times  barrel- shaped,  bilateral,  with  a  dorsal  and  ventral  symmetry,  pro- 
tected by  a  transparent  or  dense  test,  containing  cellulose,  lined  within 
by  a  tunic  surrounding  the  body-cavity.  Two  openings  in  the  test,  one 
oral,  the  other  atrial ;  mouth  leading  into  a  capacious  pharyngeal  res- 
piratory sac,  opening  posteriorly  by  an  oesophagus  into  a  stomach,  which 
is  provided  with  a  liver;  intestine  flexed,  vent  opening  near  the  oesophagus, 
the  fences  passing  into  an  atrium  or  cloacal  space,  and  thence  out  of  the 
atrial  opening.  Nervous  system  bilateral,  forming  a  double  ganglio- 
nated  chain  (Appendicularia),  but  usually  reduced  to  a  single  ganglion, 
situated  within  the  tunic  between  the  two  openings  ;  a  tubular  heart,  open- 
ing at  each  end,  lodged  in  a  sinus-system,  and  its  beatings  often  reversed, 
the  blood  flowing  in  and  out  at  either  end.  Sexes  usually  united  ;  in  some 
forms  asexual  individuals ;  reproducing  by  eggs  or  budding  partheno- 
genetically,  or  by  gemmation. 

Order  I.  Ascidiacea.  —  Body  sac-like,  subspherical,  usually  sessile, 
sometimes  stalked,  simple  or  compound,  minute  individuals 
growing  in  a  common  mass  ;  the  oral  and  atrial  openings 
contiguous  ;  often  a  complete  metamorphosis.  (Appendicu- 
laria, Botryllus,  Amarcecium,  Clavellina,  Perophora,  As- 
cidia,  Boltenia,  Pyrosoma). 

Order  2.  Thaliacea—  Body  barrel-shaped  ;  free-swimming,  test  thick, 
hyaline  ;  with  circular  muscular  bands ;  respiratory  sac 
widely  open  ;  reproducing  by  alternation  of  generations. 
(Salpa,  Doliolum), 


216  ZOOLOGY. 

Laboratory  Work. — The  Tunicates  can  well  be  studied  only  in 
a  living  state  ;  or  sections  of  hardened  SalpaB  may  be  made.  The 
young,  caught  with  the  tow-net,  should  be  immediately  examined,  as 
they  are  very  short-lived.  Delicate  sections  of  hardened  eggs  and 
larvae  are  made  with  great  difficulty,  but  are  necessary  to  examine  in 
connection  with  the  living  more  or  less  transparent  animals. 


CLASS  VII. — NEMERTINA  (Nemertean  Worms). 

General  Characters  of  Nemerteans. — The  Nemertean 
worms  occur  abundantly  under  stones,  etc.,  between  tide- 
marks  and  below  low-water  mark  ;  they  are  of  various  col- 
ors, dull  red,  dull  green  and  yellowish,  and  are  distinguished 
by  the  soft,  very  extensile,  more  or  less  flattened,  long  and 
slender  body,  which  is  soft  and  ciliated  over  the  surface, 
the  skin  being  thick  and  glandular.  A  few  forms,  such  as 
Prorhynchus  (Fig.  141),  live  in  fresh  water. 

The  mouth  forms  a  small  slit  on  the  ventral  surface  im- 
mediately behind  the  aperture  for  the  exit  of  the  proboscis. 
The  oesophagus  leads  to  a  large  digestive  tract,  ending  pos- 
teriorly with  an  anus,  and  often  with  short  lateral  ceeca.  In 
Pelayonemertes  and  Avenardia  the  numerous  cceca  are  much 
branched. 

The  nervous  system  is  quite  simple,  consisting  of  two 
ganglia  in  the  head  united  by  a  double  commissure ;  from 
each  ganglion  a  thread  composed  of  nerve  fibres  and  ganglion 
cells  passes  back  to  the  end  of  the  body. 

While  the  Nemerteans  are  much  like  the  flat  worms, 
most  of  them  approach  the  Annulata,  such  as  the  earth- 
worm, in  their  highly  complicated  circulatory  system,  which 
is  composed  of  a  series  of  closed  contractile  vessels.  There 
are  three  great  longitudinal  trunks,  one  median  and  two 
lateral,  and  connecting  with  each  other.  The  blood  is  pale, 
rarely  red,  with  corpuscles.  Another  feature  characteristic  of 
many  Nemerteans  is  the  "proboscis,"  nothing  like  it  being 
found  in  other  worms.  Along  the  back  of  the  head-end  is 
a  special  muscular  sheath  containing  the  complicated  probos- 
cis, which  is  extended  through  a  pore  situated  above  the 
mouth.  The  sheath  contains  a  corpusculated  fluid,  and 


DEVELOPMENT  OF  NEMERTEANS. 


both  the  sheath  and  proboscis  lie  between  the  commissures 
of  the  ganglia  in  the  front  part  of  the  head. 

The  ovaries  and  testes  are  situated  in  sacs 
on  each  side  of  the  digestive  canal.  The 
sexes  are  distinct,  with  the  exception  of  cer- 
tain species  of  Borlasia.  The  breeding  sea- 
son is  from  March  to  April,  while  others 
spawn  all  summer.  The  eggs  are  ejected 
from  lateral,  pale,  minute  openings,  and  the 
species  may  be  either  oviparous  or  ovovivipa- 
rous.  These  worms  when  molested  often 
break  into  fragments  ;  in  such  cases  each 
piece  is  capable  of  reproducing  the  entire  ani- 
mal and  all  its  internal  organs. 

The  JSTemerteans  present  a  great  range  of 
variation  in  their  mode  of  development.  In 
the  simplest  mode  of  growth  the  young  is  a 
ciliated  oval  form,  without  any  body-cavity. 
In  others  there  is  a  body-cavity,  but  the  larva 
is  minute  and  ciliated,  and  attains  the  adult 
form  by  direct  growth.  In  still  another  spe- 
cies (Nemertes  communis)  the  embryo  is  a 
ciliated  gastrula,  but  leaves  the  egg  in  the 
adult  form.  In  others  there  is  a  complete 
and  most  interesting  metamorphosis.  In 
several  Nemertean  worms  the  egg  undergoes 
total  segmentation,  leaving  a  segmentation- 
cavity.  ^The  next  occurrence  is  the  separa- 
tion  of  a  one-layered  ciliated  blastoderm,  the 
ectoderm,  which  invaginates,  forming  the 
primitive  digestive  cavity,  from  which  the 
stomach  and  oesophagus  are  formed. 

,  /••-M-I-TT  -iji  f 

larva  (  originally  described  under  the  name  01  above  the 

7->  .7  .  7  .        \     .  ,     ,         ,       ,  ,         .,  .    ,     -.     gus,  which  ends  in  a 

Jrilidium)    is  now   helmet  -  shaped,   ciliated,  Blind  sac  at  y  ; 
with  a  long  lash  (flagellum)  attached  to  the 
posterior  end  of  the  body.     (Fig.  142.) 


Figi4i.  —  Pro- 


oae 
The  *,  style  in  the  pro- 

boscis    situated 


ov, 
of 


After  swimming  about  on  the  surface  of  ^Sfaur~Af  ter  °e~ 


the  sea  a  while,  the  Nemertes  begins  to  grow 
out  from  near  the  oesophagus  of  the  Pilidium. 


On  each 


218 


ZOOLOGY. 


side  of  the  base  of  the  velum  (v)  of  the  Pilidium  ap- 
pear two  thickenings  of  the  skin,  one  pair  in  front, 
the  other  behind;  these  thickenings  push  inwards,  and 
are  the  germs  of  the  anterior  and  posterior  end  of  the 
future  worm.  The  anterior  pair  become  larger  than 

the  posterior  ;  the  part  of 
the  disk  next  to  the  reso- 
phagus  thickens  ;  at  the 
same  time  the  alimentary 
canal  of  the  Pilidium 
grows  smaller,  and  only  a 
narrow  slit  remains.  The 
disks  now  divide  into  two 
layers,  the  outer  much 
thicker  than  the  inner. 
Soon  the  anterior  pair  of 
disks  unite,  and  the  head 
of  the  worm  is  soonformed, 
when  the  elliptical  outline 

Fig.  143.— Larva  or  "Pilidium"  of  Nemer-    nf  fi1p    flnf   Wftrm    is    indi- 
tes, with  the  worm  growing  in  it.    «,  velum  ;     OI   tlie    naL   WO1 


Nemertean  worm.—  cated,  and  appears  some- 
what  as  in  Fig.  142.  The 
yolk  mass,  with  the  alimentary  canal  of  the  Pilidium, 
is  taken  bodily  into'  the  interior  of  the  Nemertes,  the 
Pilidium-skin  falls  off,  and  the  worm  finally  seeks  the 
bottom. 

The  free-swimming  larvae  of  other  Nemerteans  are  very 
closely  similar  to  those  of  the  Annelids,  so 
that  from  this  fact  and  the  nature  of  the 
highly  developed  circulatory  system,  the 
Nemerteans  have  been  removed  from  the 
neighborhood  of  the  flat  worms,  and  placed 
near  the  Balanoglossus  and  Gephyrea,  as 
well  as  the  leeches. 

Fig.  143.  —  Tetra-       Order  1.  Auopla. — In  this  group  the  pro- 
woTmfmSiTfieerdean  boscis  is  without  a  style.     The  species  of 
Linens  and  Meckelia   are,  in   some   cases, 
very  long.      MecJcelia  ingens   Leidy  is  2^  centimetres   (an 
inch)  wide,  and  attains  a  length  of  4  metres  (15 J  feet).     It 


BALANOGLOSSUS.  219 

lives  under  stones  at  or  below  low-water  mark  on  the  coast 
of  ISTew  England  southwards  to  South  Carolina. 

Order  2.  Enopla. — In  the  members  of  this  group  the 
proboscis  is  furnished  with  a  style.  Eepresentatives  of  the 
order  are  the  species  of  Tetrastemma  (T.  serpentinum 
Girard,  Fig.  143)  and  of  N emeries.  The  former  is  a  little 
yellowish  worm,  common  under  stones  on  the  coast  of  New 
England  between  high  and  low- water  mark  ;  it  has  a  slightly 
marked  head  with  four  dark  eye-specks. 


CLASS  VII.— NEMERTINA. 

Body  ribbon-like  or  cylindrical,  soft,  extensible,  ciliated  externally,  witli 
a  proboscis  in  a  sheath  opening  by  a  pore  situated  above  the  mouth.     Cir- 
culatory system  approaching  that  of  the  Annulata.    Sexual  organs,duct- 
less  sacs ;  either  with  or  witlwut  a  metamorphosis. 
Order  1.  Anopla. — Proboscis  without  a  style.     (Lineus,  Meckelia.) 
Order  2.  Enopla. — Proboscis  with  a  style.     (Nemertes,    Malacobdella.) 


CLASS  VIII. — EKTEROPKEUSTA  (Acorn-tongue  worms.} 

General  Characters  of  the  Enteropneusta — The  re- 
markable worm,  Balanoglossus  (Fig.  144),  the  type  of  this 
class,  combines  characters  peculiar  to  itself,  with  features 
reminding  us  of  the  Nemerteans,  Annelids,  Tunicata,  and 
even  the  vertebrate  Amphioxus,  while  its  free-swimming 
larva,  before  its  history  was  known,  was  supposed  to  be  a 
young  Echinoderm.  It  is  therefore,  like  some  other  worms, 
a  synthetic  or  generalized  type. 

Balanoglossus  aurantiacus  (Girard,  Fig.  144)  is  a  long, 
cylindrical,  soft,  fleshy  worm,  footless,  without  bristles,  but 
with  a  large,  soft,  whitish  tongue-shaped  proboscis  in  front, 
arising  dorsally  within  the  edge  of  the  collar  surrounding 
the  mouth.  At  the  beginning  of  the  digestive  canal  is  a 
series  of  sac-like  folds,  of  which  the  upper  or  dorsal  portion 
is  respiratory,  and  separated  by  a  constriction  from  the  lower, 


ZOOLOGY. 

which  is  digestive,  and  leads  directly  to  the  intestine  behind. 
This  pharyngeal  respiratory  portion  of  the  digestive  canal  has 
on  each  side,  in  each  segment,  a  dorsal  sac,  the  two  commu- 
nicating along  the  median  line  of  the  body.  The  dorsal  re- 
spiratory sacs  bear  in  their  walls  a  delicate  ehitinous  gill- 
support  or  arch.  Between  the  gill-arches,  forming  nnmerons 
lamellae,  are  a  series  of  slits,  leading  on  each  side  to  open- 
ings (spiracnla)  situated  dorsally.  The  water  passes  through 
the  mouth  into  each  gill-sac,  and  out  by  the  spiracles.  Xo 
nervous  system  has  yet  been  discovered.  There  is  a  dorsal 
yeasel,  which  sends  branches  to  the  respiratory  sacs,  and  a 


Balatogiomu.  a,  anas ;  ft,  branch  of  water-TMcu- 
pore  (d);  «,  eye-speck ;  g,  gills  ;  A,  hart ;  i,  in- 
bandfrom  the  eye  to  the  water-Taaadar  tube :  o, 

ttuTcanal;  «,  lappet  of  stomach ;  i^,  asal  bod  of 

ventral  vessel.     The  worm  lives  in  sand  at  low-water  mark 
from  Cape  Ann  to  Charleston,  S.  C. 

The  life-history  of  this  worm  is  most  interesting.  The 
young,  originally  described  under  the  name  of  Tornaria, 
was  supposed  to  be  an  Echinoderm  larva,  though  it  closely 
resembles  the  larval  Gephyrea  and  Annelidas.  It  is  a  trans- 
parent, minute,  ciliated,  slender,  somewhat  bell-shaped  form 
(Fig.  145),  with  black  eye-specks.  When  transforming  to 
the  worm  condition,  a  pair  of  gills  arise  on  sac-like  out- 
growths of  the  oesophagus,  and  afterwards  three  additional 


ANATOMY  OF  PKA8GOLOSOMA.  221 

pairs  with  their  external  slits  arise,  somewhat  as  in  Ascidians. 
The  entire  Tornaria  directly  transforms  into  the  worm,  the 
transitional  period  being  very  short.  The  body  lengthens, 
the  collar  and  proboscis  deyelop,  and  the  worm  eventually  is 
as  seen  in  Fig.  144 ;  afterwards  the  body  lengthens,  the  end 
tapering  and  becoming  much  coiled. 


CLASS  VIIL— ENTEROPNEUSTA. 

Footless,  smoothbodied  worm*;  with  no  bristles,  a  large  exserted  soft 
JUshy  proboscis  ;  breathing  by  a  series  of  dorsal  respiratory  sacs  opening 
into  the  digestive  canal,  and  communicating  externally  by  spiracles  ;  witk 
a  metamorphosis.  (BalanoglosBus.) 


CLASS  IX. — GEPHYREA  (Star-worms). 

General  Characters  of  the  Gephyreans.— The  most  acces- 
sible type  or  representative  of  this  small  but  interesting  group 
of  worms  is  a  large,  smooth,  cylindrical  worm  from  six  to 
ten  inches  long,  which  is  common  in  sand  or  sandy  mud  at 
low-water  mark.  It  is  the  Sipunculus  or  Phascolosoma 
Gouldii  Diesing,  and  from  its  abundance  and  large  size,  as 
well  as  the  ease  with  which  it  can  be  preserved  in  spirits,  is  an 
excellent  subject  for  the  laboratory,  serving  as  an  example  of  a 
very  aberrant  type  of  worm  as  compared  with  the  earth- 
worm, or  with  a  Nereis.  The  body  is  as  smooth  as  a  pipe- 
stem,  and  about  that  size,  unarmed,  with  a  circle  of  numer- 
ous small,  flat,  foliaceous  tentacles  around  the  month.  On 
laying  open  the  body  from  the  head  to  the  extremity  (Fig. 
146),  the  body-walls  are  seen  to  be  lined  with  fine  longi- 
tudinal flat  muscles,  with  two  unequal  pairs  of  large  white 
retractor  muscles,  the  anterior  third  of  the  body  being 
highly  retractile.  The  intestinal  part  is  found  to  float  free- 
ly, though  anteriorly  attached  to  the  walls  by  a  few  muscu- 
lar threads,  in  the  capacious  body-cavity,  and  is  usually  full 
of  fine  mud.  The  oesophagus  is  long  and  slender,  situated 
between  the  shorter  pair  of  retractor  muscles ;  behind  the 


222 


ZOOLOGY. 


insertion  of   the  muscles  it  enlarges,    but  there  is  no  true 
stomach  ;  it  is  about  twice  the  length  of  the  body,  and  is  bent 

and  twisted  on  itself,  ending 
dorsally  in  a  vent  marked  by  an 
external  wart,  on  the  anterior 
third  of  the  body.  Near  this 
point  is  situated  a  pair  of  large, 
long,  slightly  twisted  segmental 
organs(s)the  free  ends  of  which 
flare  slightly.  The  nervous 
system  (n)  forms  an  cesophageal 
ring,  and  from  it  passes  a  well- 
marked  ventral  single  cord, 
from  which  at  short  intervals 
pass  off  small  short  lateral 
nerves.  The  vascular  system 
is  represented  by  a  circular 
vessel  lying  next  to  the  ner- 
vous oasophageal  ring,  sending 
branches  into,  or  at  least  in 
communication  with,  the  cavi- 
ties of  the  tentacles,  and  from 
the  ring  passing  along  and  in- 
timately connected  with  the  di- 
gestive tract,  forming  a  ruffle- 
like  organ  (v),  ending  at  a  point 
nearly  opposite  the  vent  (a). 
Prof.  Greef  finds  that  the  vas- 
cular system  of  EcMurus  con- 
sists of  two  main  vessels,  i.  e., 
_  a  dorsal  and  a  ventral  vessel  ; 

Fig.  i4fl.-A^my  of  Pkascotosoma  the  f  ormer  extending  along  the 

alimentary  canal,  and    ending 


The 


muscles  ;  pr,  two  long  retractor  mus-  a  branch  to  the  proboscis,  where 

cles;   v,  next  to  a  dark  line  the  right  .            .     ,        , 

side  of  the  long  oesophagus  indicating  it     divides    lllto    two    branches, 

the  water-vascular  tube  ;    n,  nervous  ,            ...              .  ,       .  ,                      , 

cord  ;  «,  segmental  organs  ;  the  long,  each   uniting   With    the   VClltral 

twisted  intestine  returns,  ending  at  a.  -i        mi        -i-,       -i    •           -i          -i 

Natural  size.-Drawn  by  J.  S.  Kings-  VCSSel.       The   blood  IS   pale  yel- 

lowish,  with  corpuscles. 


blood-system  of   the  Gephyrea,  then,  is  homologous   with 


DEVELOPMENT  OF  GEPHYREANS.  223 

that  of  the  Annulata.  There  is  in  Phascolosoma  no  true 
ovary,  but  the  eggs  float  in  masses  in  the  capacious  body- 
cavity,  the  animal  being  a  hermaphrodite. 

Phoronis  is  from  the  highly  developed  crown  of  long, 
slender  tentacles,  and  its  complicated  blood-system,  remark- 
ably like  the  Serpulcs,  with  which  Annelids  it  is  by  some 
authors  associated.  The  alimentary  tube,  however,  is  like 
that  of  Pliascolosoma,  the  intestine  folded  and  ending  next 
to  the  mouth.  ]Slo  nervous  system  has  been  detected.  A 
pulsating  artery  is  attached  to  the  upper  side  of  the  long 
oesophagus,  and  its  branches  go  into  the  tentacles  from  an 
oesophageal  ring.  "  Two  venous  trunks  open  from  the  sin- 
uses above  and  behind  the  arterial  branches,  and  then  pro- 
ceed downwards,  half  encircling  the  oesophagus,  till  they 
unite  in  a  large  vessel  on  its  neural  surface."  (Dyster.) 
This  worm  is  minute,  about  four  millimetres  in  length,  and. 
lives  in  a  tube  buried  in  holes  in  rocks.  It  has  a  strong  re- 
semblance to  a  Polyzoon,  but  connects  the  Gephyrea  with 
the  true  Annelids. 

In  the  Sipunculus-like  worm  Phascolosoma,  and  in  Pho- 
ronis, there  is  a  well-marked  metamorphosis,  and  the  larvae 
are  somewhat  like  those  of  Annelids.  The  larva  of  Phas- 
colosoma is  cylindrical,  the  head  small,  with  a  circle  of  cilia, 
but  there  are  no  arms  as  in  the  larva  of  the  Phoronis. 

The  earliest  observed  stage  of  Phoronis  *  is  a  free-swim- 
ming larva,  the  body  transparent,  ciliated,  with  an  umbrella- 
like  expansion  on  the  head,  covering  the  region  of  the  mouth, 
while  the  end  of  the  body  is  truncated.  At  this  stage  it  is  a 
true  Cephalula,  like  that  of  Echinoderms  and  worms.  Af- 
terwards four  projections  arise  at  the  end  of  the  body,  and 
twelve  long,  arm-like  projections  grow  out,  the  larval  form 
now  being  fully  attained.  In  this  condition  it  was  de- 
scribed as  a  mature  animal  under  the  name  Actinotrocha. 

When  the  Actinotrocha  is  about  to  transform  into  a  Pho- 
ronis the  end  of  the  intestine  bends  up,  opening  outward 

*  In  our  Outlines  of  Comparative  Embryology  this  account  of  the 
metamorphosis  of  Phoronis  is  by  mistake  regarded  as  descriptive  of 
Sipunculus  on  pp.  157,  158,  under  Development.  The  word  Phoronis 
on  those  pages  should  be  substituted  for  Sipunculus. 


224 


ZOOLOGY. 


near  the  mouth.  The  umbrella  is  gradually  withdrawn  into 
the  mouth,  so  that  eventually  only  a  crown  of  short  tooth- 
like  projections  surrounds  the  mouth.  Finally  the  whole 
umbrella  is  swallowed,  the  arms  at  the  end  of  the  body  dis- 
appearing, while  the  end  of  the  intestine  projects  far  out 
from  the  body  behind  the  mouth.  By  this  time  the  Phoro- 
nis  form  is  clearly  indicated,  the  body  being  long  and  slen- 
der and  the  mouth  surrounded  by  a  crown  of  short  tentacles, 
the  end  of  the  intestine  being  entirely  withdrawn  within  the 
body.  These  changes  are  rapidly  effected.  The  larva  of 
EcMurus  is  formed  on  the  Annelid  type. 

In  Phascolosoma  ccementarium  (Quatrefages),  the  body  is 
much  shorter  than  in  P.  Goul- 
dii ;  the  worm  lives  in  compara- 
tively deep  water  (10  to  50  fath- 
oms), in  dead,  deserted  shells, 
building  out  the  aperture  by  a 
conical  tube  of  sand.  In  Sipun- 
culus  (Syrinx)  the  tentacles  are 
fringed  or  lobed.  It  does  not 
occur  in  American  waters. 

In  EcJiiurus  the  intestine  ends 
at  the  end  of  the  body,  and  there 
is  a  circle  of  bristles  at  the  pos- 
terior end,  while  Bonellia  differs 
in  having  an  enormous  proboscis, 
and  only  a  few  bristles  near  the 
head.  In  Bonellia  viridis  Rol. 
of  the  Mediterranean  (Fig.  147), 
the  proboscis  is  deeply  forked; 
the  intestine  is  very  long,  convo- 
,,  luted,  and  into  the  cloaca  empty 

Fig.    147.— Bonellia   mndis  ;    the  J-    J 

proboscis  coiled  several    times.     »,  two  excretory  Ol'gailS.      The  OVary 

lore  end  of  the  proboscis  ;  s,  «',  fnr-  .  -,-,•-,  -i  •    i     •       ,  -, 

row  in  the  proboscis  ;  i,i,  digestive  is  a  COrd-llke  Organ,  which  in  the 
canal :  m,  mesenterial  threads  (only  .  ;r  ,  ..  ,  .  „  , 

shown  on  the  anterior  end  of  the  di-  posterior  part  01  the  body  IS  last- 

rofvVSci;^rrrducf-Aftree;  ened  to  the  intestine. 

Lacaze-Duthiers;  from  Gegenbaur.  Clmtoderma   nitldulum  Loven 

occurs  in  20-40  fathoms  off  the  coast  of  Europe  and 
Northern  New  England.  The  body  is  long,  cylindrical,  and 


CHARACTERISTICS  OF  GEPHYREANS.  225 

covered  with  slender,  firm,  calcareous  spines.  It  lias  no 
tentacles,  a  straight  digestive  canal,  the  vent  being  terminal, 
and  two  internal  gill-sacs,  with  external  lamellate  gills. 

Instead  of  a  single  nervous  cord,  as  usual  in  the  Gephyrea, 
in  ClicBtoderma  there  are  two  separate  nerve-cords,  one  on 
each  side  of  the  body.  The  Gephyrea  were  formerly  asso- 
ciated with  the  Echinoderms,  but  the  resemblance  is  only  a 
superficial  one. 


CLASS  IX.— GEPHYREA. 

Body  long,  cylindrical,  smooth,  or  spiny,  or  provided  with  bristles,  not 
segmented;  usually  a  large  proboscis,  but  none  in  Phascolosoma;  vent 
either  terminal  or  situated  dorsally  on  the  anterior  end  of  the  body.  A 
true  blood-system  homologous  loith  that  of  the  Annulata.  Bisexual  or 
hermaphroditic  ;  young  of  the  Annelid  type,  undergoing  a  metamorpho- 
sis. (Chsetoderma,  Phascolosoma,  Sipunculus,  Bonellia,  Ecliiurus,  and 
Pkoronis.) 

Laboratory  Work. — The  common  star-worm,  Phascolosoma,  is  one 
of  the  easiest  worms  to  dissect,  as  it  can  be  readily  laid  open  with 
the  scissors,  and  the  skin  pinned  down  on  the  bottom  of  the  dissecting 
trough,  when  the  parts  can  be  readily  distinguished,  its  structure  being 
unusually  simple. 


CLASS  X. — ANNULATA  (Leeches,  Earth-ivorms,  and 
Sea-ivorms). 

General  Characters  of  the  Annulata — This  group,  rep- 
resented by  the  leeches,  earth-worms,  and  nereids  or  bristled 
sea-worms,  tops  the  series  of  the  classes  of  worms,  and  in 
the  highly  specialized,  regularly  segmented  bodies,  with  their 
sense-organs  and  highly  differentiated  appendages,  stand 
nearer  the  Crustacea  and  Insecta  than  any  other  class  of  in- 
vertebrate animals,  their  internal  organization  on  the  whole 
being  nearly  as  complicated. 

Reference  to  the  accompanying  diagram  (Fig.  148)  will 
show  the  general  relation  of  the  organs  of  an  Annelid  to  the 
body-walls,  as  compared  with  corresponding  parts,  when  seen 
in  sections  of  Amphioxus  and  a  fish. 


226  ZOOLOGY. 

The  student,  in  familiarizing  himself  with  the  structure 
and  mode  of  growth  of  the  leech,  the  common  earth-worm 


Fig.  148.—  Transverse  section  of  a  vrarm,  of  AmpMoxus,  and  a  higher  vertebrate 
contrasted.  «,  skin  ;  6,  dermal  connective  layer;  c,  muscles;  d,  segmental  organ  ;  h, 
arterial,  and  i,  venous  blood-vessel  ;  g,  intestine  ;  I,  notochord.—  After  Haeckel. 


and  the  Nereis,  will  obtain  a  good  idea  of  the  essential  char- 
acteristics of  the  entire  class. 

Order  1.  Hirudinea.  —  In  the  leech  (Fig.  149),  Hirudo 
medicinalis  Linn.,  the  type  of  the  first  and  lower  order,  the 
body  is  somewhat  flattened  and  divided  into  numerous  short, 
indistinctly  marked  segments,  not  bearing  any  bristles  or 
appendages.  The  head  is  small,  with  no  appendages,  bear- 
ing five  pairs  of  simple  eyes,  while  each  end  of  the  body  ter- 
minates in  a  sucker.  The  mouth  is  armed  internally  with 
three  pharyngeal  teeth  arranged  in  a  triradial  manner,  so 
that  the  wound  made  in  the  flesh  of  persons  to  whom  the 
leech  is  applied  consists  of  three  short,  deep  gashes  radiating 
from  a  common  centre.  The  stomach  (Fig.  150)  is  large, 
with  large  lateral  diverticula  or  lobes,  while  the  intestine  is 
small.  The  nervous  system  consists  of  a  "  brain"  and  ven- 
tral ganglionated  cord. 

The  vascular  system  is  complicated,  consisting  of  a  median 
dorsal  and  a  ventral  vessel,  and  two  lateral  vessels  ;  all  these 
anastomose  or  interbranch,  and  the  blood  which  courses 
through  them  is  red,  but  is  said  to  contain  no  corpuscles. 

The  segmental  organs,  so  characteristic  of  the  Annulata, 
are  well  developed  in  the  leech,  consisting  of  about  seventeen 
pairs  of  tubes  opening  at  one  end  at  regular  intervals  on  the 
under  side  of  the  body,  and  ending  in  a  non-ciliated  coil 
(Fig.  149,  r)  in.  the  leech,  or  in  the  smaller  fish-leech,  Clep- 
sine,  open  into  the  venous  sinus  by  ciliated,  open  mouths. 


ANATOMY  OF  THE  LEECH. 


227 


FIG.  150. 

Fig.  149.— Anatomy  of  the  medicinal  leech  ; 
opened  from  below,  a,  h,  buccal  sucker  ;  b,  infra- 
cesophageal  irauglioa;  e,c,e,  ventral  ganglia;  d,  last 
ganglion  ; ./'./,./'.  commissures  joining  the  ganglia  ; 
(Ji  fit  ffi  nerves  of  sense  and  locomotion  ;  i,  oesopha- 
gus ;  #,  A1,  &,  A;,  t\\c.  dilatations  or  coeca  of  the  stom- 
ach ;  m,  the  last  of  these  lobes  or  coeca ;  p, p,  intes- 
tine lying,  as  well  as  the  stomach,  above  the  ner- 
vous chain  ;  q,  rectum  ;  ?%  /•,  r,  scgmental  organs  ; 
s,  pouch  ;  x,  sheath  of  z,  coupling  organ  ;  t,  right 
epididymis ;  A,  A,  A,  spermatic  cords;  B,  B,  S, 
testes ;  D,  matrix ;  E,  E,  ovaries  ;  w,  end  of  ovi- 
duct; v,  sucker. 

Fig.  150. — Digestive  canal  of  the  same  ;  a,  5,  ft, 
6,  b,  the  stomach  and  its  lateral  lobes  or  coeca;  d}  c, 
the  two  large  coeca  which  extend  along  each  side 
of  the  intestine  et  e;  /,  rectum.— After  Gervais  and 
Van  Beneden. 


Fia.  149. 


228  ZOOLOGY. 

The  leech  is  hermaphroditic,  while  in  certain  allied  forms 
(Histriobdella,  etc.)  the  sexes  are  distinct. 

The  eggs  of  leeches  are  laid  in  sacs,  or,  as  in  Clepsine,  the 
fish-leech,  are  covered  with  a  transparent  fluid  substance, 
which  hardens  and  envelops  the  eggs.  The  Clepsine  re- 
mains over  the  eggs  to  protect  them  until  they  hatch  ;  and 
the  young,  after  exclusion,  fix  themselves  to  the  under  side 
of  the  parent,  and  are  thus  borne  about  until  they  are  fully 
developed  and  able  to  provide  for  themselves  (Whitman*). 
The  changes  in  the  egg  of  Clepsine,  after  fertilization,  are 
very  complicated,  and  have  been  described  by  Whitman. 
The  egg  subdivides  into  a  bilateral  mass  of  cells  called  a 
blastula  ;\  agastrula,  and  finally  a  "neurula"  stage,  charac- 
terized by  the  formation  of  a  "primitive  band"  like  that  of 
insect  embryos.  Soon  after  attaining  the  latter  stage  the 
embryo  hatches  and  attaches  itself  to  its  parent.  The  mouth 
is  then  formed,  the  nervous  system^  arises  from  the  ecto- 
derm, the  segments  are  indicated,  the  original  number  being 
thirty-three,  the  segmental  organs  develop  from  the  meso- 
derm  at  about  the  time  of  hatching,  and  about  six  days  after 
the  neurula  leaves  the  egg  the  eyes  become  visible.  The 
innermost  germ-layer  (endoderm)  does  not  arise  until  eight 
days  after  hatching,  and  by  this  time  the  digestive  tract  is 
perfected ;  the  muscular  walls  of  the  alimentary  canal  being 
derived  from  the  mesoderm. 

*  The  Embryology  of  Clepsine.  By  C.  O.  Whitman.  Quarterly 
Journal  of  Microscopical  Science.  July,  1878. 

f  Whitman  states  that  a  morula,  as  defined  by  Haeckel,  does  not 
occur  in  the  developmental  history  of  Clepsine,  and  he  states  that  when 
the  cleavage  process  of  the  egg  has  been  carefully  studied  it  has  been 
found  to  result  in  the  production  of  a  bilateral  germ  or  blastula,  and 
not  a  morula.  "  '  A  solid  sphere  of  indifferent  cells'  is,  to  say  the 
least,  a  very  improbable  form,  so  improbable  that  its  existence  may  be 
held  questionable  until  established  by  positive  evidence.  The  doubt 
is  all  the  more  justifiable,  as  more  careful  investigation  has  in  many 
cases  already  shown  that  the  so-called  mulberry  stage  is  not  a  morula, 
but  a  blastula  or  even  a  gastrula."  (Whitman.) 

$  There  is  originally  a  pair  of  ganglia  in  each  of  the  thirty-three 
segments  ;  four  of  these  are  consolidated  into  the  suboesophageal  gan- 
glia, eight  in  the  ganglia  of  the  disk,  and  four  in  the  terminal  ganglia 
of  the  body.  (Whitman.) 


EMBRYOLOGY  OF  LEECHES.  229 

The  early  phases  in  the  embryological  development  of  the 
leech  (Clepsine)  strongly  resemble  those  of  corresponding 
stages  in  the  vertebrates,  according  to  a  number  of  observers. 
The  origin  of  the  germ-bands,  the  presence  of  the  primitive 
streak  as  well  as  the  mode  of  cleavage,  and  the  formation  of 
the  gastrula*  and  neurula,  show  that,  up  to  a  comparatively 
late  period  of  embryonic  life,  some  worms  (Annulata)  and 
the  Vertebrates  travel  along  the  same  developmental  path. 
As  observed  by  Whitman,  the  neurula  of  the  chick,  or  of 
the  fish,  belongs  to  the  same  type  as  that  of  Clepsine. 
Whether  the  Vertebrates  ever  descended  from  the  worms  or 
any  other  type  of  Invertebrates  or  not,  it  is  a  matter  of  fact 
that  there  is  an  essential  unity  in  organization  and  mode  of 
early  development  in  all  the  Metazoa,  or  three-germ-layered 
animals,  and  that  the  vertebrates  are  probably  only  a  very 
highly  specialized  group  of  animals,  a  branch  of  the  same 
genealogical  tree  from  which  have  sprung  the  only  less 
generalized  groups  or  branches  of  Mollusca,  Annulata,  and 
Arthropoda.  Certainly  the  division  of  the  animal  kingdom 
into  Vertebrates  and  Invertebrates,  however  useful,  is  essen- 
tially artificial  and  misleading.  Hence  it  follows  that  a 
study  of  the  Annulata,  as  well  as  other  types  of  worms,  must 
prove  to  be  fruitful  in  valuable  results,  and  lead  to  what 
may  seem  startling  conclusions. 

Order  2.  Annelides. — To  this  order  belong  the  earth- 
worm and  sea-worms.  The  structure  of  the  common  earth- 
worm (Lumbricus  terrestris  Linn.,  Fig.  151)  is  essentially 
like  that  of  the  leech.  Externally  the  body  is  cylindrical, 
many-jointed,  the  joints  or  segments  much  more  distinct 
than  in  the  leech,  and  internally  there  are  septa,  or  thin 
muscular  partitions,  between  them.  The  mouth  is  small, 
forming  an  opening  on  the  under  side  of  the  first  segment. 
On,  or  next  to,  the  twenty-ninth  to  the  thirty-sixth  seg- 
ments in  Lumbricus  terrestris  is  a  flesh-colored  swollen 
portion  called  the  cingulum  or  clitellum. 

The  earth-worm  is  able  to  climb  perpendicularly  up  boards, 

*  Professor  His  admits  that  the  bird  passes  through  a  stage  compar- 
able with  the  gastrula  of  other  animals.  (Whitman,  p.  94.) 


230 


ZOOLOGY. 


etc.,  as  well  as  over  the  ground, -by  minute,  short,  curved 
setae  or  bristles,  which  are  deeply  inserted  in  the  muscular 
walls  of  the  body,  and  arranged  in  four  rows  along  each  side 
of  the  body.  The  alimentary  canal  is  straight,  the  stomach 
has  three  pairs  of  small  lateral  blind  sacs  (cceca),  and  the 
intestine,  which  is  externally  tubular,  contains  a  thick  inter- 
nal sac-like  fold  called  a  typhlosole. 

The  segmental  organs  are  highly  convoluted  tubes,  a  pair 
to  each  segment  of  the  body,  except  a  few  near  the  head, 
and  opening  internally  with  ciliated  funnels  and  externally 
in  minute  pores  situated  along  the  under  side  of  the  body. 
The  earth-worm  is  monoecious  (hermaphroditic). 

The  oviducts  open  in  the  fourteenth  segment,  and  the 
seminal  ducts  (vasa  deferentia)  in  the  fifteenth.  Between 
the  ninth  and  tenth,  and  the  tenth  and  eleventh  segments 
are  the  four  openings  of  the  seminal  receptacles  (receptacula 
seminis).  Pairing  is  reciprocal  (see  Fig,  151),  each  worm 
fertilizing  the  eggs  of  the  other ;  they  pair  in  June  and  July 
in  the  night-time.  The  eggs  of  the  European  Lumbricus 

rubellus  Grube  are  laid 
in  dung,  a  single  egg  in 
a  capsule ;  L.  ayricola 
lays  numerous  egg-cap- 
sules, each  containing 
sometimes  as  many  as 
fifty  eggs,  though  only 
three  or  four  live  to  de- 
velop. The  development 
of  the  earth-worm  is  like 
that  of  the  leech,  the 
germ  passing  through  a 

morula   (blastula),   gas- 
Fig.  151.—  Earth-worms  pairing.    After  Curtis.  \ 

a,  embryo  (blastula)  soon  after  segmentation  of  trilla  and  neurula  Stage, 
the  yolk";  ft,  embryo  further  advanced;  o,  mouth;  ,,  111.1 

c,  embryo  still  older ;    k,  primitive  streak ;   d,    the    WOrm,    When    hatch- 
ing, resembling  the  pa- 
rent, except  that  the  body  is  shorter  and  with  a  much  less 
number  of  segments. 

While  the  earth-worms  are  in  the  main  beneficial,  from 
their  habit  of  boring  in  the  soil  of  gardens  and  ploughed 


ANATOMY  OP  NEREIS 


231 


lands,  bringing  the  subsoil  to  the  surface  and  allowing  the 
air  to  get  to  the  roots  of  plants,  they  occasionally  injure 
young  seedling  cabbage,  lettuce,  beets,  etc.,  drawing  them 
during  the  night  into  their  holes,  oi4  uprooting  them. 

The  next  and  highest  type  of  Annulata  is  the  common 
sea-worm  of  our  coast,  Nereis  virens  Sars.  It  lives  between 
tide-marks  in  holes  in  the  mud,  and  can  be  readily  obtained. 
The  body,  after  the  head,  eyes,  tentacles  and  bristle-bearing 
feet  have  been  carefully  studied,  can  be  opened  along  the 
back  by  a  pair  of  fine  scissors  and  the  dorsal  and  ventral  red 
blood-vessels  with  their  connecting  branches  observed,  as 
well  as  the  alimentary  canal  and  the  nervous  system. 

The  anatomy  of  this  worm  has  been  described  by  Mr.  F. 
M.  Turnbull.  It  is  very  voracious,  thrusting  out  its  pharynx 
and  seizing  its  prey  with  its  two  large  pharyngeal'  teeth.  It 
secretes  a  viscid  fluid  lining  its  hole,  up  which  it  moves, 
pushing  itself  along 
by  its  bristles  and 
ligulae.  At  night, 
probably  during  the 
b  r  e  e  d  i  n  g  season, 
they  leave  their 
holes,  swimming  on 
the  surface  of  the 
water. 

The  body  consists 
of  from  one  hundred 
to  two  hundred  seg- 
ments. The  head 
consists  of  two  seg- 
ments, the  anterior 
and  buccal,  the  for- 

•  ,i      £ 
Ilier    With    four    eyes 

on/l       fwrt       via  1*1*0     nf 
and      tWO       pairs     01 

antprmjp        Thp    SPP 
mse'  " 

ond  segment  bears 
four  antennae  (tentacular  cirri).  Each  of  the  other  segments 
bears  a  pair  of  paddle-like  appendages  (rami),  which  may  be 
best  studied  by  examining  one  of  the  middle  segments  which 


Fig.  152.— Vertical  section  through  the  integumert 
of  an  Annelid  (Spkcerodorum).  c,  thick  curicular 
layer  with  the  pore-canals  ;  m,  muscular  layer ;  mf, 
muscles  of  the  bristles,  «,  which  retract  the  central 
foot-lobe,  while  others  pass  to  its  dorsal  glandular 
projection,  d.—  After  Gegenbaur. 


232  ZOOLOGY. 

has  been  separated  from  the  others.  For  the  finer  structure 
of  the  body-walls  see  Fig.  152. 

The  alimentary  canal  consists  of  a  mouth,  a  pharynx 
armed  with  two  large  teeth  and  much  smaller  ones.  The 
pharynx  is  entirely  everted  during  the  act  of  taking  its  food. 
Into  the  oesophagus  empty  two  large  salivary  glands ;  the 
remainder  of  the  alimentary  canal  is  straight  and  tubular. 
The  circulatory  system  is  very  complicated  ;  it  is  closed  and 
the  blood  is  red.  Both  the  dorsal  and  ventral  vessels  are 
contractile,  the  blood  flowing  forward  in  the  dorsal  vessel, 
and  backward  in  the  ventral  vessel.  The  two  small  vessels, 
one  on  each  side,  in  each  segment  of  the  body,  branch  off 
from  the  ventral  vessel  and  subdivide,  each  sending  a  branch 
to  the  ventral  ramus  of  the  foot  of  the  segment  behind,  and 
another  larger  branch  around  the  intestine  to  the  dorsal  ves- 
sel, receiving  also,  on  its  way,  a  vessel  from  the  upper  ramus 
of  the  foot  of  its  own  segment.  "  Besides  these  principal 
lateral  vessels,  there  are  five  other  vessels  on  each  side 
in  each  segment,  coming  from  the  ventral  vessel.  These 
form  a  loose  but  regular  net-work  that  surrounds  the  in- 
testine and  is  connected  with  five  other  convoluted  vessels, 
which  join  the  dorsal  vessel.  This  net-work  on  the  intestine 
probably  supplies  the  hepatic  organ  with  material  for  its 
secretion,  and  very  likely  may  receive  nutritive  material  from 
the  digested  food."  (Turnbull. ) 

The  blood  is  aerated  in  the  finer  vessels  of  the  oar-like  feet 
and  in  those  situated  about  the  alimentary  canal.  The 
nervous  system  consists  of  the  "  brain"  and  ventral  double 
ganglionated  cord. 

The  sexes  of  Nereis  virens  are  separate ;  the  eggs  during 
the  breeding  season  fill  the  body-cavity,  and  pass  out  through 
certain  of  the  segmental  organs,  which  act  as  oviducts,  while 
others,  probably  the  more  anterior  ones,  are  excretory,  like 
the  kidneys  of  vertebrates,  as  urea  has  been  detected  in  them. 
These  organs  are  situated  at  the  base  of  the  lower  ramus  of 
each  foot.  In  some  species  of  the  Capitellidce  Eisig  has  found 
that  it  is  normal  for  several  segmental  organs  to  be  present 
in  a  single  segment. 

While  the  mode  of  development  of  our  Nereis  has  not 


Off  ANNELIDS. 


233 


been  studied,  the  eggs  are  probably  laid  in  masses  between 
tide-marks,  and  the  young,  when  hatched,  swim  freely  on 
the  surface  of  the  sea.  The  eggs  of  other  worms  are  carried 
about  in  lateral  pouches.  The  germ  undergoes  a  cleavage 
phase  and  a  gastrula  stage.  We  have  observed,  in  Salem 
harbor,  the  development  of  Polydora  (probably  P.  ciliatum 
Clap.)  which  maybe  found  in  August,  in  all  stages,  on  the 


Fig.  153.— .4,  earliest  observed  stage  of  Polydord",  St  Cephalula  stage  ;   C and  Z>, 
later  stages.— Author  del. 

surface  of  the  water.  When  first  observed  (Fig.  153,  A)  the 
body  was  spherical,  with  a  short,  broad  intestine,  and  two 
sets  of  large  locomotive  bristles.  It  then  passed  into  the 
cephalula  state,  the  head  clearly  indicated  and  forming  a 
large  hood.  This  stage  is  seen  at  B,  which  represents  the 
under  side  of  the  cephalula,  the  mouth  being  situated  be- 
tween the  two  large  ciliated  flaps  (like  the  velum  of  larval 
mollusks)  of  the  hood ;  the  body  is  now  segmented,  with  a 
third  set  of  bristles  and  a  band  of  cilia  on  the  penultimate 
segment ;  afterwards  as  at  (7,  dorsal  view,  additional  rings 
are  present ;  the  eyes  are  distinguishable,  and  there  are  two 
more  sets  of  bristles.  The  new  segments  are,  as  usual  in  all 


234 


ZOOLOGY. 


articulates,  interpolated  between  the  penultimate  and  ter- 
minal segments  of  the  body.  At  D,  the  body  is  many- 
jointed,  the  tentacles  well  developed,  the  large  temporary 
bristles  have  been  discarded,  and  the  worm  can  be  identified 
as  a  young  Polydora. 

It  is  probable  that  Polydora  is  hatched  as  a  trochosphere 
like  that  of  Polyzoa,  Brachiopoda  and  certain  mollusks. 
The  young  Terebrellides  Stroemii,  and  of  Lumbriconereis, 
are  at  first  trochospheres,  i.  e.,  the  free-swimming 
germ  is  spherical,  with  a  zone  of  cilia,  two  eye- 
spots,  and  no  bristles.  Thus  the  earliest  stages  of 
Polyzoa,  Brachiopoda,  Lamellibranchiata,  Gastro- 
poda, and  even  of  a  Cephalopod  (Fig.  220),  Nemer- 
tina,  and  Annelides  are  almost  identical.  Farther 


Fig.   154.- 

,arva     of 

Phyllodoce.— 


Larva    of  a]ong  m  their  developmental  history,  the  cepha- 


A.Ag-  Ma  of  the  Annelides  (Fig.  153,  A,  B,  and  155), 
is  like  that  of  certain  Echinoderms  (Fig.  155), 
Gepliyrea,  Polyzoa,  Brachiopoda,  and  Mollusca.  It  may 
here  be  observed  that  the  free-swimming  larvae  of  these  types 
of  invertebrate  animals  are  the  young  of  more  or  less  seden- 


Fig.  155.— Cepbalula  stage  of  Echinoderms  and  Worms,  lateral  view.  A,  Hoio- 
thnrian,  Zf,  Star-fish,  C7,  Z>,  of  Annelides. 

o,  mouth ;  i,  stomach  ;  a,  vent ;  0,  prseoral  ciliated  band,  in  B,  C,  D,  independent ; 
in  A  surrounding  an  oral  region. — From  Gegenbaur. 

tary  parents.  In  this  way  the  species  becomes  widely  dis- 
tributed through  the  action  of  the  marine  currents,  and  too 
close  in-and-in  breeding  is  prevented. 

Certain  Annelides  sometimes  multiply  by  self -division,  the 
process  being  called  strobilation.    This  is  commonly  observed 


BUDDING   OF  ANNELIDS, 


235 


in  the  fresh-water  worm  Nais,  also  in  Syllis  and  Myrianida, 
as  well  as  in  Filograna,  Protula,  etc.  Autolytus,  a  com- 
mon worm  on  the  coast  of  New  England,  produces  one  gen- 
eration by  budding  (parthenogenesis).  There  is,  in  fact,  an 
alternation  of  generations,  an  asexual  Autolytus,  giving 


FIG.  156. 


FIG.  157. 

Fig.    156—  Clymenella  torquata.— After  Verrill. 

Fig.  \yi.-Amphilrite  cirrata,  enlarged  twice.    ft,  branchia ;  c,  uncini,  enlarged  500 
diameters.— After  Holmgren. 

rise  to  a  brood  of  males  and  females,  the  sexual  and  asexual 
forms  being  so  unlike  each  other  as  to  have  been  mistaken 
for  different  species  and  even  genera. 

In  Syllis  and  allies  certain  long,  slender  processes  of  the 


236 


ZOOLOGY. 


feet  are  jointed,  thus  anticipating  the  jointed  appendages  of 
the  Crustacea  and  Insects. 

The  Annelides  are  divided  into  two  suborders.  The  first 
suborder,  Oligochceta,  comprises  Lumbricus,  Nais,  etc.,  while 
the  second  suborder,  Ch6&topoda,embi:a,cesSyUis,  Autolytus, 
Nereis,  Polydora,  Aphrodite,  and  Polynoe,  which  are  free- 
swimming,  while  the  tubiculous  worms  which  respire  by  spe- 


FIG.  158. 

Fig.  158.— Cistenides  Gouldii,  and  its  tube.— After  Verrill. 
Fig.  159. — JSuchone  elegam,  enlarged. — After  Verrill. 


FIG.  159. 


cial  branchiae,  or  gills,  on  the  head,  live  in  tubes  of  sand  or 
in  limestone  shells.  Those  which  live  in  sand  or  mud-tubes 
are  Cirratulus  (Fig.  160),  Clymene and  Clymenella  (Fig.  156), 
which  has  no  branchiae,  Amphitrite  (Fig.  157),  Terelrella, 
Cistenides  (Fig.  158),  Sabella,  and  Euchone,  (Fig.  159), 
while  Protula,  Filograna,  Serpula  and  Spirorbis  secrete 
more  or  less  coiled  limestone  tubes.  The  large  solid  shells 
of  the  Serpulae  assist  materially  in  building  up  coral  reefs, 


SILURIAN  WORM  TRACKS. 


23? 


especially  on  the  coast  of  Brazil.  The  minute  nautilus-like 
shells  of  Spirorbis  live  attached  to  the  fronds  of  sea-weeds, 
especially  the  different  kinds  of  Fucus. 


Fig.  160.—Cirratulus  grandis.— After  Verrill. 

Many  sea-worms  are  highly  phosphorescent, the  light  emit- 
ted being  intensely  green.  The  tracks  of  worms  like  the 
Nereis  of  to-day  occur  in  the  lower  Silurian  slates ;  their 
bristles,  however,  were  spinulose,  as  in  the  larval  worms. 
Thus  the  type,  though  highly  specialized,  has,  unlike  most 
specialized  groups,  a  high  antiquity,  the  specialized  Anne- 
lides  existing  side  by  side  with  the  generalized  Polyzoa  and 
Brachiopoda.  At  the  present  time  the  Annelides  are  widely 
distributed  in  the  seas  of  the  globe,  the  tropical  forms  being 
exceedingly  abundant  among  coral  stocks  and  in  sponges, 
while  the  arctic  seas  abound  with  Annelid  life.  They  also 
sparingly  exist  at  great  depths,  one  species  of  a  worm  allied 


ZOOLOGY. 


to  Clymene,  having  been  dredged  by  the  Challenger  Expedi- 
tion at  the  enormous  depth  of  over  three  miles  (about  5000 
metres). 


CLASS  X.— ANNULATA. 

Body  long,  bilaterally  symmetrical,  cylindrical,  consisting  of  numerous 
segments,  either  unarmed,  or  more  usually  provided  with  setae  alone  or  with 
setae  and  paddle-like  appendages  (rami).  Head  simple,  with  a  few  simple 
eyes,  or  provided  with  tentacles  (antennce)  alone,  or  with  tentacles  and  bran- 
chiae. An  ever 'sible  pharynx,  armed  with  teeth,  usually  present.  Alimentary 
system  straight,  the  tubular  stomach  sometimes  sacculaUd;  vent  always 
situated  in  the  last  segment  of  the  body.  Nervfras  sysUm  well  developed, 
consisting  of  a  brain  and  ventral  ganglionated  cord.  Circulatory  system 
closed,  with  a  dorsal  and  ventral  and  lateral  vessels  connected  by  anasto- 
mosing branches  in  nearly  each  segment.  A  system  of  numerous  paired 
segmental  organs.  Sexes  united  or  separate.  Embryo  passing  through 
a  cleavage-stage  (morula  orblastula),  gastrula,  sometimes  a  neurula  stage, 
and  after  hatching,  development  is  either  direct  or  there  is  a  marked  met- 
amorphosis, the  larva  passing  through  a  trochosphere  and  cephalula 
stage. 

Order  I.  Hirudinea. — Body  unarmed,  finely  segmented  ;  with  a  pos- 
terior sucker.  (Hirudo,  Nephelis.) 

Order  2.  Annelides.—  Suborder  1.  Oligochceta  (Lumbricus,  Nais).  Sub- 
order 2. — Ohcetopoda  (Arenicola,  Syllis,  Autolytus,  Aphro- 
dite, Polynoe,  Amphitrite,  Terebrella,  Sabella,  Serpula, 
Spirorbis). 

TABULAR  VIEW  OP  THE  CLASSES  OF  WORMS  (VERMES). 
Annulata. 

Brachiopoda. 


Enteropneusta. 
Tunicata. 


Gephyrea. 


Polyzon. 


Nemertina. 


Rotatoria. 
I 


Nematelminthes. 


Platyhelminthes. 


VERMES, 


ANNUL  AT  A.  239 

Laboratory  Work. — Worms  should  be  dissected  at  once  after  be- 
ing killed  by  ether  or  in  alcohol,  before  the  circulation  has  ceased  ; 
and  transverse  sections  made  to  observe  the  relation  of  the  appendages 
to  the  body- walls,  and  of  the  different  systems  within  the  body- walls. 
The  worms  should  also  be  hardened  in  alcohol,  and  thin  sections 
stained  with  carmine  be  made  for  histological  study.  A  portion  of  the 
worm  can  be  put  in  paraflme  and  sliced  by  hand  with  the  razor  or  by 
the  microtome. 


Amphitrite  ornata- 


CHAPTER  VI. 

BKANCH  VI.—  MOLLUSCA. 

General  Characters  of  Mollusks. — The  characters  which 
separate  this  branch  from  the  others,  especially  the  Vermes 
arc  much  less  trenchant  than  those  peculiar  to  other  groups 
of  the  same  rank,  and  indeed  the  author  only  retains  the 
Mollusks  as  a  special  branch  in  deference  to  the  general 
usage  of  zoologists,  believing  that  the  Mollusca  are  probably 
only  a  highly  specialized  group  of  Vermes,  where  they  were 
originally  placed  by  Linnaeus,  and  bearing  much  the  same 
relation  to  the  true  worms  as  do  the  Rotator  ia,  the  Tuni- 
cata,  the  Brachiopoda,  etc.  It  will  be  seen  from  the  fol- 
lowing account  of  the  mollusks,  that  they  travel  along,  appar- 
ently, the  same  developmental  road  as  the  genuine  worms, 
and  then  suddenly  diverge,  and  the  divergence  is  not  an  ad- 
vance in  a  parallel  direction,  but  if  anything  the  road  turns 
back,  or,  to  change  the  simile,  the  branch  of  the  genea- 
logical tree  bends  downwards.  It  is,  and  always  has  been, 
extremely  difficult  to  define  the  Mollusca,  their  original 
bilateral  symmetry  being  partially  effaced  in  most  of  the 
Gastropoda  and  in  some  Lamellibranchs,  i.  e.,  in  those 
Gastropods  with  a  spirally-twisted  shell  like  the  snail,  or  in 
fixed  bivalve  forms  like  the  oyster,  etc.  The  Mollusca  are 
usually  defined  as  animals  with  laterally  symmetrical,  un- 
jointed  bodies  protected  by  a  shell,  with  a  foot  or  creeping 
disk,  and  usually  with  lamellate  gills,  which  are  folds  of  the 
mantle  or  body-walls.  The  special  organs  characterizing 
the  Mollusks  are  the  foot  and,  in  nearly  all  except  Lamel- 
libranchs, the  odontophore ;  but  the  foot  of  a  snail  is  simply 
a  modification  of  the  under  lip,  and  in  reality  in  many  forms 
Imt  a  specialized  ventral  surface,  as  is  that  of  certain  non- 
segmented  worms,  like  the  Planarians  and  Nemerteans ;  while 


MORPHOLOGY  OF  MOLLUSKS.  241 

the  odontophore  or  lingual  ribbon,  often  absent,  is  appar- 
ently a  modification  of  the  pharyngeal  teeth  of  Annelides. 
Mollusks  in  general  have  a  heart  consisting  of  a  ventricle 
and  one  or  two  auricles,  and  in  this  respect  they  are  more 
like  the  Vertebrates  than  other  invertebrated  animals ;  the 
highly  developed  eye  of  the  squids  and  their  imperfect  car- 
tilaginous brain-box  are  also  special  characters  analogous  to 
the  eye  and  brain-box  of  Vertebrates.  Still  these  features 
are  not  homologous  with  the  corresponding  parts  in  the 
Vertebrates,  and  we  have  already  seen  that  the  Tunicata, 
and  even  the  Annelides,  are  much  more  closely  allied  to  the 
Vertebrata  than  are  the  Mollusks,  which  should,  perhaps, 
be  interpolated  between  the  Brachiopods  and  Tunicates. 
The  affinities  of  the  Mollusks  are,  then,  decidedly  with  the 
worms,  rather  than  with  the  Vertebrates. 

That  the  Mollusca  are  a  highly  specialized  and  compara- 
tively modern  group  is  shown  by  the  fact  that  they  began 
to  abound  after  the  Brachiopods  had  had  their  day  in  the 
Silurian  seas,  and  had  begun  to  decay  and  die  out  as  a  type  ; 
the  shelled  Mollusca  supplanted  the  shelled  Vermes  or  Brachi- 
opods. For  the  upper  Silurian  period,  and  those  later,  the 
Mollusks  prove  useful  as  geological  time-marks,  especially  in 
the  Cainozoic  period,  and  so  much  so  that  Lyell  based  his 
divisions  of  Tertiary  time  mainly  on  the  shells  which  abound 
in  Tertiary  strata. 

Although  morphologically  the  shell  of  a  Mollusk  is  not 
the  most  important  feature  of  the  animal,  it  is  very  charac- 
teristic of  them  and  of  great  use  in  distinguishing  the  species 
of  existing,  but  more  especially  of  fossil,  forms ;  still  it  is 
liable  to  great  variation,  and  mollusks  of  quite  different 
families,  and  even  orders,  sometimes  have  shells  much  alike, 
so  that  the  characters  of  shells,  like  many  of  those  drawn 
from  the  peripheral  parts  of  the  body,  are  liable  oftentimes 
to  mislead  the  student.  That  the  Mollusca  are  a  highly 
specialized  group  is  also  seen  by  the  enormous  number  of 
existing  species,  and  their  wide  geographical  and  bathymet- 
rical  range.  There  are  about  20,000  living  and  19,000 
fossil  species  known,  and  the  group  ranks  next  to  the 
winged  insects,  also  a  comparatively  recent  and  highly 


ZOOLOGY. 

specialized    group,   in  the   number    of    species   and    indi- 
viduals. 


CLASS  I. — LAMELLIBRANCHIATA  (Acephala,  Bivalves). 

General  Characters  of  Lamellibranchs — This  group  is 
represented  by  the  oyster,  clam,  mussel,  quohog,  scallop, 
etc.  By  a  study  of  the  common  clam  ( My  a  arenaria  Linn. ) 
one  can  obtain  a  fair  idea  of  the  anatomy  of  the  entire  class, 
as  it  is  a  homogeneous  and  well-circumscribed  group.  The 
clam  is  entirely  protected  by  a  pair  of  solid  limestone  shells, 
connected  by  a  hinge,  consisting  of  a  large  tooth  (in  most 
bivalves  there  are  three  teeth)  and  ligament  (Fig.  161  0  L). 
The  shells  are  equivalve,  or  with  both  valves  alike,  but  not 
equilateral,  one  end  (the  anterior)  being  distinguishable  from 
the  other  or  posterior,  the  clam  burrowing  into  the  mud  by 
the  anterior  end,  that  containing  the  mouth  of  the  mollusk. 
The  hinge  is  situated  directly  over  the  heart,  and  is  there- 
fore dorsal  or  haBmal.  On  the  interior  of  the  shells  are  the 
two  round  muscular  impressions  made  by  the  two  adductor 
muscles  and  the  pallial  impression,  parallel  to  the  edge  of 
the  shell,  made  by  the  thickened  edge  of  the  mantle.  On 
carefully  opening  the  shell,  by  dividing  the  two  adductor 
muscles,  and  laying  the  animal  on  one  side  in  a  dissecting 
trough  filled  with  water,  and  removing  the  upper  valve,  the 
mantle  or  body-walls  will  be  disclosed ;  the  edge  is  much 
thickened,  while  within,  the  mantle  where  it  covers  the  el- 
liptical rounded  body  is  very  thin.  The  so-called  black 
head,  or  siphon,  is  divided  by  a  partition  into  two  tubes,  the 
upper,  or  that  on  the  hinge  or  dorsal  side,  being  excurrent, 
the  lower  and  larger  being  incurrent — a  current  of  sea-water 
laden  with  minute  forms  of  life  passing  into  it.  Each  orifice 
is  surrounded  with  a  circle  of  short  tentacles.  This  siphon 
protrudes  through  a  slit  in  the  mantle-edge,  and  is  very  ex- 
tensible, as  seen  in  Fig.  161,  A  ;  it  is  extended,  when  the 
clam  is  undisturbed,  from  near  the  bottom  of  its  hole  to  the 
level  of  the  sea-bottom.  In  the  fresh-water  mussel  ( Unio, 
Fig.  162)  the  two  siphonal  openings  are  above  the  level  of 


AN  A  TO  MT  OF  THE  CLAM. 


243 


the  sandy  bottom  of  the  water,  when  the  mussel  is  plough- 


ing its  way  through  the 
sand  with  its  tongue- 
shaped  foot,  which  is  a 
muscular  organ  attach- 
ed to  the  visceral  mass, 
and  is  a  modification 
of  the  under  lip  of  the 
larval  mollusk.  In  the 
foot  is  an  orifice  for 
the  passage  in  and  out 
of  water,  but  the  spurt- 
ing of  water  from  the 
clam's  hole,  observed 
in  walking  over  the 
flats,  is  the  stream  eject- 
ed from  the  siphon. 
The  inflowing  currents 
of  water  pass  from  the 
inner  end  of  the  mus- 
cular siphon  below  the 
lenticular  visceral  mass 
to  the  mouth,  which  is 
situated  at  the  anterior 
end  of  the  shell,  oppo- 
site the  siphon.  The 
opening  is  simple,  un- 
armed, without  lips, 
and  often  difficult  to 
detect.  On  each  side 
of  the  mouth  is  a  pair 
of  flat,  narrow-pointed 
appendages  called  pal- 
pi. The  digestive  ca- 
nal passes  through  a 
dark  rounded  mass, 
mostly  consisting  of 
the  liver,  covered  ex- 
ternally by  the  ovarian 


Fig.  161.— A,  Mya  arenarii  with  its  siphons  ex- 
tended ;  in  its  natural  position  in  the  mud  head- 
end downwards  ;  B,  transverse  section  of  the  shell, 
showing  the  position  of  the  spring  opening  the 
shell;  M,  adductor  mn PC! e  ;  the  ligament  represent- 
ed by  dark  mass  ;  C,  section  of  TTnio,  showing  the 
position  of  the  spring  to  open  the  shell ;  L,  liga- 
ment ;  I),  ideal  transverse  section  of  Unio;  /,  intes- 
auricle  ;  £,  gills  ; 


244  ZOOLOGY. 

masses.  There  is  no  pharynx  armed  with  teeth  as  in  the 
Cephalophora  and  Cephalopoda,  but  the  oesophagus  leads  to 
a  tubular  stomach  and  intestine,  the  latter  loosely  coiled  sev- 
eral times  and  then  passing  straight  backwards  along  the  dor- 
sal side  under  the  hinge  and  directly  through  the  ventricle  of 
the  heart,  ending  posteriorly  opposite  the  excurrent  division 


Fig.  162.—  Unto  complanatus,  partly  buried  in  the  sand,  the  siphonal  openings 
above  the  level  of  the  river-bottom. — After  Morse. 

of  the  siphon.  Through  the  visceral  mass  passes  a  curious 
slender  cartilaginous  rod,  whose  use  is  unknown,  unless  it  be 
to  support  the  voluminous  viscera.  The  gills  or  branchiae  are 
four  large,  broad,  leaf -like  folds  of  the  mantle,  two  on  a  side, 
hanging  down  and  covering  each  side  of  the  visceral  mass 
(Fig.  161,  D,  G).  The  heart  (Fig.  163)  is  contained  in  a  deli- 
cate  sac,  called  the  pericardium,  and  is  situ- 
ated  immediately  under  the  hinge  ;  it  consists 
of  a  ventricle  and  two  auricles  ;  the  former  is 
easily  recognized  by  the  passage  through  it  of 
the  intestine  (Fig.  161,  D,  v),  usually  colored 
Pig.  163.— Heart  dark,  and  by  its  pulsations.  The  two  wing- 
like  auricles  are  broad,  somewhat  trapezoidal 
in  form.  Just  behind  the  ventricle  is  the  so- 
called  "aortic  bulb."  The  arterial  system  is 
quite  complicated,  as  is  the  system  of  venous  sinuses,  which 
can  be  best  studied  in  carefully  injected  specimens.  At  the 
base  of  the  gills,  however,  is  the  pair  of  large  collective 
branchial  veins.  The  kidney,  or  "organ  of  Bojanus,"  is  a 
large  dulky  glandular  mass  (Fig.  164,  4)  lying  below  but  next 


ANATOMY  OF  THE  CLAM.  245 

to  the  heart ;  one  end  is  secretory,  lamellar  and  glandular, 
communicating  with  the  pericardial  cavity,  while  the  other 
is  excretory  and  opens  into  the  cavity  of  the  gill.  The 
nervous  system  can  be,  with  care  and  patience,  worked  out 
in  the  clam  or  fresh-water  mussel.  In  the  clam  (My a  arena- 


Fig.  164,— Circulatory  system  of  Anodonta,  a  fresh-water  mussel,  after  Bojanus. 
1,  ventricle ;  2,  arterial  system ;  14  and  15,  veins  which  follow  the  horder  of  the 
mantle.  The  veins  lead  the  blood  in  part  directly  towards  the  organ  4,  which  is  the 
kidney  or  "organ  of  Bojanus,"  and  in  part  to  the  venous  sinus  of  the  upper  surface 
of  this  organ  ;  5,  veins  which  carry  back  the  blood  from  the  gills,  the  rest  going  to 
the  sinus,  6,  where  arise  the  branchial  arteries ;  7,  8,  the  branchial  veins,  and  9,  the 
gill.— From  Gervais  et  Van  Beneden. 

ria,  Fig.  165)  it  consists  of  three  pairs  of  small  ganglia, 
one  above  (the  "  brain")  and  one  below  the  oesophagus  (the 
pedal  ganglia)  connected  by  a  commissure,  thus  forming  an 
cesophageal  ring ;  and  at  the  middle  of  the  mantle,  near  the 
base  of  the  gills,  is  a  third  pair  of  ganglia  (parieto-splanch- 
nic),  from  which  nerves  are  sent  to  the  gills  and  to  each 
division  of  the  siphon.  This  last  pair  of  ganglia  can  be 
usually  found  with  ease,  without  dissection,  especially  after 
the  clam  has  been  hardened  in  alcohol.  The  ear  of  the  clam 
is  situated  in  the  so-called  foot ;  it  bears  the  name  of  otocyst 
(Fig.  166,  i),  and  is  connected  with  a  nerve  sent  off  from  the 
pedal  ganglion.  It  is  a  little  white  body  found  by  laying 
open  the  fleshy  foot  through  the  middle.  Microscopic  ex- 
amination shows  that  it  is  a  sac  lined  by  an  epithelium,  rest- 
ing on  a  thin  nervous  layer  supported  by  an  external  coat  of 
connective  tissue.  From  the  epithelium  spring  long  hairs  ; 
the  sac  contains  fluid  and  a  large  otolith.  The  structure  of 
this  octocyst  may  be  considered  typical  for  Invertebrates. 


246 


ZOOLOGY. 


The  ovaries  or  testes,  as  the  sex  of  the  clam  may  be,  are 
bilaterally  symmetrical,  blended  with  the  wall  of  the  visce- 
ral or  liver-mass,  and  are  yellowish.  The  genital  openings 


Fig.  165. — Nervous  system  of  the  clam,  natural  size,  a,  cesophageal  ganglion  ;  J, 
commissure  anterior  to  the  mouth ;  c,  pedal  commissure  ;  d,  pedal  ganglia  ;  e,  parieto- 
splanchnic  commissures ;  /,  parieto-splanchnic  ganglia  ;  g,  branchial  nerves  ;  h,  I,  pal- 
lia! nerves  ;  i,  siphonal  nerves  ;  k.  anal  nerves  •  m,  nerves  to  the  anterior  adductor. — 
Drawn  by  W.  K.  Brooks. 

are  paired  and  lie  near  the  base  of  the  foot.  Both  eggs  and 
semen  arise  from  the  epithelium  of  the  sexual  glands.  The 
eggs  pass  out  into  the  body-cavity,  or  accumulate  between  the 


ANATOMY  OF  THE  CLAM. 


247 


gills,  where  the  embryos  in  some  species  partially  develop. 

Impregnation  probably    takes   place    within  the  branchial 

chamber,  the  spermatozoa  being 
swept  in  with  the  respiratory 
current,  and  coming  in  contact 
Avith  the  eggs  as  they  are  dis- 
charged. 

An  excellent  general  view  of 
the  relation  of  parts  to  the 
body  -walls  and  shell  may  be 
seen  by  hardening  a  clam,  or 
better  a  fresh  -water  mussel, 
Unio  (see  Fig.  161,  D)  in  alco- 
hoi,  and  then  making  trans- 

vprsp  qpofions  A  Sfotiori  ran 
veibC  ^OUOIlb.  A.  bLCUOj 

be  floated  off  in  water  and  ex- 

amined  with  a  lens-   The  P61" 

the  pedal  muscles.—  Drawn  by  w,  K.  feet  bilateral  symmetry  of  parts 

Brooks.  J  J 

will  thus  be  seen. 
The  above  description  will  answer  for  the  majority  of  la- 


Fi 


and  ot-> 


cysts  (cars)  of  the  clam,  magnified  10 
diameters     d   pedal  ganglia-  e,  pedal 


1; 


Pig.  167.—  Lima  Mans,  flying  through  the  water,  its  long  numerous  filaments  ex- 
tended.—From  Brehm's  "  Thierleben." 

mellibranchiate  mollusks  ;  in  the  oyster  (Ostrcea)  or  in  A  no- 


248  ZOOLOGY. 

mia  the  shell  is  inequilateral,  one,  usually  the  lower,  being 
fixed  to  some  object,  and  the  intestine  does  not  pass  through 
the  ventricle ;  in  Area  the  ventricle  is  double.  In  Lucina 
and  Corbis  there  is  but  one  gill  on  each  side,  and  in  Pecten, 
Spondylus  and  Trigonia  the  gills  are  reduced  to  comb-like 


Fig.  M)8.—Mytilis  edufis,  common  mussel,  a,  mantle  ;  J,  foot;  c,  byssns ;  d  and  e, 
muscles  retracting;  the  foot ;  /,  mouth  ;  a,  palpi ;  ht  visceral  mass  •  i,  inner  gill ;  j, 
outer  gill.— From  Brehm's  "  Thierlebem"  t 

processes.  There  are  usually  no  eyes  present ;  in  the  scallop 
(Pecten),  however,  there  is  a  row  of  bright  shining  eyes 
with  tentacles  along  the  edge  of  the  mantle,  and  contrary 
to  the  habits  of  most  bivalves,  the  scallop  can  skip  over  the 
surface  of  the  water  by  violently  opening  and  shutting  its 
shell.  Trigonia  is  also  capable  of  leaping  a  short  distance  ; 
while  Lima  (Fig.  167)  is  an  active  flyer  or  leaper.  Ostrea  and 
Cyclas  are  dioecious,  while  many  mollusks  are  monoecious  or 
hermaphroditic.  The  foot  varies  much  in  form,  in  the 
mussel  (Mytilus,  Figs.  168,  169),  Pinna,  Cydocardia  (Car- 
dita)  (Fig.  170),  and  the  pearl-oyster  it  is  finger-shaped  and 


TYPICAL  BIVALVES. 


249 


grooved,  with  a  gland  for  secreting  a  bundle  of  threads,  the 
byssus,  by  means  of  which  it  is  anchored  to  the  bottom. 


Fra.  170. 

Fig.  169.— Mytilus  edulis,  common  mussel,  with  its  fringe  expanded,  and  anchored 
by  its  byssus. — After  Morse. 
Fig.  170. — Cyclocardia  novanglicb,  natural  size. — After  Morse. 

The  foot  in  the  quohog  (Fig.  171  A,  Venus  mercenaries), 
Mulinia  (171  B)  and  Clidiopliora  (Fig.  172)  is  large,  these 


Fig.  171  A.—  Venus  mercenaria,  quohog,  natural  size,  with  the  foot  and  siphons. 
Fig.  171  B.—Mactra  (Mulinia)  lateralis,  natural  size.— After  Verrill. 

mollusks  being  very  active  in  their  movements.  In  Glyci- 
meris  (Fig.  173)  the  fringe  is  toothless,  much  as  in  the 
oyster.  In  Mactra  (Fig.  174)  the  middle  tooth  is  large,  the 


250 


ZOOLOGY. 


corresponding  cavity  large  and  triangular.     In  Saxioava  and 
Panopcea  (Fig.  175),  the  pallial  line  is  represented  by  a 

row  of  dots.  In  Macoma  (Fig. 
176)  the  siphons  are  very  long. 
Lithodomus,  the  date  shell, 
one  of  the  mussels,  bores  into 
corals,  oyster  shells,  etc. ;  the 
common  Saxicava  excavates 

^J^S!S^^!rWMa^  na~  holes  in  mud  and  soft  lime- 

stone,    as    does    Gastrochcena, 

Pliolas  and  Petricola.     Many  boring   Lamellibranchs  are 
said  to  be  luminous. 


Fig.  VtZ—Glydmeris  siliqua,  natural  size.— After  Morse. 

A  very  aberrant  form  of  bivalve  mollusk  is  Clavagella,  in 
which  the  shell  is  oblong,  with  flat  valves,  the  left  cemented 
to  the  sides  of  a  deep  burrow.  The  tube  is  cylindrical, 
fringed  above  and  ending  below  in  a  disk,  with  a  minute 
central  fissure,  and  bordered  with  branching  tubules.  In 
Aspergillum,  the  watering-pot  shell,  the  small  bivalve  shell 
is  cemented  to  the  lower  end  of  a  long  shelly  tube,  closed 
below  by  a  perforated  disk  like  the  "rose"  of  a  watering- 
pot. 

The  most  aberrant  Lamellibranch  is  the  ship-worm,  Teredo 
navalis  Linn.  (Fig.  179).  This  species  is  now  cosmopolitan, 
and  everywhere  attacks  the  hulls  of  ships  and  the  piles  of 
wharves.  It  is  one  of  the  most  destructive  to  human  inter- 
ests of  all  animals.  The  body  is  from  one  to  two  feet  long, 
slender,  fleshy ;  it  lives  in  a  burrow  lined  with  limestone, 
while  the  shell  itself  is  globular,  and  lodged  at  the  farther 


FORMATION  OF  PEARLS. 


351 


end  of  the  tube  or  burrow.  The  mantle  lobes  of  the  ani- 
mal are  united,  with  a  minute  opening  for  the  foot,  which  is 
small,  sucker-like.  The  heart  is  not  pierced  by  the  intes- 


Fig.  174.— Mactra  walls,  natural  size.— After  Morse. 

tine,  while  the  siphons  are  very  long  and  furnished  with 
two  shelly  styles. 

Pearls  are  sometimes  produced  in  bivalve  shells  by  particles 
of  sand  getting  in  between  the  mantle  and  the  shell,  which 


Fig.  175.— Panopcea  arctica,  natural  size.— After  Morse. 


cause  an  irritation  to  the  tissues  of  the  mantle  and  the  for- 
mation of  a  nacreous  shelly  matter  around  the  nucleus. 
Excellent  pearls  are  sometimes  found  in  fresh-water  rnussels; 


252  ZOOLOGY. 

but  the  purest  occur  in  the  pearl  oyster,  Meleagrina  marga- 
ritifera  (Linn.),  which  occurs  at  Madagascar,  Ceylon,  the 
Persian  Gulf,  and  at  Panama.  The  largest  pearl  known 
measures  two  inches  long,  four  round,  and  weighs  1800 
grains.  All  bivalves  pass  through  a  metamorphosis  after 
birth.  The  development  of  the 
oyster  is  a  type  of  that  of  most  La- 
mellibranchs. 

A  single  oyster  may  lay  about 
2,000,000  eggs  ;  they  are  yellow,  and 
after  leaving  the  ovary  are  for  the 

m°st  Part  retained  among  the  8ills- 
In  Europe  the  oyster  spawns  from 

June  till  September ;  during  their  growth  the  eggs  are  en- 
closed in  a  creamy  slime,  growing  darker  as  the  "spat"  or 
young  oyster  develops. 

The  course  of  development  is  thus :  after  the  segmenta- 
tion of  the  yolk  (morula  stage),  the  embryo  divides  into  a 
clear  peripheral  layer  (ectoderm),  and  an  opaque  inner  layer 
containing  the  yolk  and  representing  the  inner  germinal 
layer  (endoderm).  A  few  filaments  or  large  cilia  arise  on 
what  is  to  form  the  velum  of  the  future  head.  The  shell 
then  begins  to  appear  at  what  is  destined  to  be  the  posterior 
end  of  the  germ,  and  before  the  digestive  cavity  arises.  The 
digestive  cavity  is  next  formed  (gastrula  stage),  and  the  anus 
appears  just  behind  the  mouth,  the  alimentary  canal  being 
bent  at  right  angles.  Meanwhile  the  shell  has  grown  enough 
to  cover  half  the  embryo,  which  is  now  in  the  "Veliger" 
stage,  the  "velum"  being  composed  of  two  ciliated  lobes  in 
front  of  the  mouth-opening,  and  comparable  with  that  of 
the  gastropod  larvae.  The  young  oyster,  as  figured  by  Salen- 
sky,  is  directly  comparable  with  the  Veliger  of  the  Cardium 
(Fig.  177).  Soon  the  shell  covers  the  entire  larva,  only  the 
ciliated  velum  projecting  out  of  an  anterior  end  from  be- 
tween the  shells.  In  this  stage  the  larval  oyster  leaves  the 
mother  and  swims  around  in  the  water.  According  to 
Brooks  the  American  oyster  becomes  free-swimming  larva 
in  six  hours  after  the  egg  is  fertilized.  At  a  later  period  it 
becomes  fastened  to  some  rock.  The  oyster  is  said  to  be 


EMBRYOLOGY  OP  CARDIUM. 


253 


three  years  in  attaining  its  full  growth,  but  is  able  to  propa- 
gate at  the  end  of  the  first  year. 

The  development  of  the  cockle  (Cardium pygmceum),  is 
better  known.  After  passing  through  a  morula  and  gastrula 
stage,  the  embryo  becomes  ciliated  on  its  upper  surface  and 
already  rotates  in  the  shell.  On  one  side  of  the  oval  em- 
bryo is  an  opening  or  fissure,  on  the  edges  of  which  arise  two 
tubercles  which  eventually  become  the  two  "  sails"  of  the 
velum.  The  next  step  is  the  differentiation  of  the  body 
into  head  and  hind  body,  i.e.,  an  oral  (cephalic)  and  postoral 
region.  Out  of  the  middle  of  the  head  grows  a  single  very 
large  cilium,  the  so-called  flagellum  (Fig.  177  A,  fl;  v, 


ml 


Fig.  177.— The  development  of  the  cockle  Bhell  (Cardium).  A.  the  trochosphere  ; 
»,  ciliated  crown  ;  fl,  flagellum.  B,  Veliger  stage,  with  the  shell  developing  ;  «, 
velum  ;  m,  mouth  ;  ti,  liver  lobes  ;  t,  stomach  ;  {,  intestine  ;  mt,  mantle  ;  /,  foot ; 
ml,  muscle  ;  n,  nervous  ganglion.— After  Loven. 

velum).  The  shell  (B,  sh)  and  mantle  (mt;  ml,  muscle) 
now  begin  to  form.  From  the  inner  yolk-mass  are  developed 
the  stomach,  the  two  liver  lobes  (li)  on  each  side  of  the 
stomach  (t),  and  the  intestine  (i).  The  mouth  (m),  which 
is  richly  ciliated,  lies  behind  the  velum,  the  alimentary  canal 
is  bent  nearly  at  right  angles,  and  the  anus  opens  behind  and 
near  the  mouth.  The  velum  (Fig.  177  B,  v)  really  consti- 
tutes the  upper  lip,  while  a  tongue-like  projection  (B,  f)  be- 
hind the  mouth  is  the  under  lip,  and  is  destined  to  form  the 
large  unpaired  "foot,"  so  characteristic  of  the  mollusks. 
The  shell  arises  as  a  cup-shaped  organ  in  both  bivalves  and 
univalves,  but  the  hinge  and  separate  valves  are  indicated 
very  early  in  the  Lamellibranchs.  At  the  stage  represented 


254  ZOOLOGY. 

by  Fig.  177  2?,  tlie  stomach  is  divided  into  an  anterior  and 
posterior  (pylori c)  portion.  The  liver  forms  on  each  side  of 
the  stomach  an  oval  fold,  and  communicates  by  a  large  open- 
ing with  its  cavity ;  while  the  intestine  elongates  and  makes 
more  of  a  bend.  The  organ  of  hearing  then  arises,  and  be- 
hind it  the  provisional  eyes,  each  appearing  as  a  vesicle  with 
dark  pigment  corpuscles  arranged  around  a  refractive  body. 
The  nerve-ganglion  (n)  appears  above  the  stomach.  The 
two  ciliated  gill-lobes  now  appear,  and  the  number  of  lobes 
increases  gradually  to  three  or  four.  The  foot  grows  larger, 
and  the  organ  of  Bojanus,  or  kidney,  becomes  visible.  The 
shell  now  hardens  ;  the  mouth  advances,  the  velum  is  with- 
drawn from  the  under  side  to  the  anterior  end  of  the  shell. 
In  this  condition  the  Veliger  remains  for  a  long  time,  its  long 
flagellum  still  attached,  and  used  in  swimming  even  after  the 
foot  has  become  a  creeping  organ.  Latest  of  all  appears  the 
heart,  with  the  blood-vessels. 

Upon  throwing  off  the  Veliger  condition,  the  velum  con- 
tracts, splits  up  and  Loven  thinks  it  becomes  reduced  to  the 
two  pairs  of  palpi,  which  are  situated  on  each  side  of  the 
mouth  of  the  mature  Lamellibranch.  The  provisional  eyes 
disappear,  and  the  eyes  of  the  adult  arise  on  the  edge  of  the 
mantle. 

In  the  fresh-water  mussels  ( Unio)  the  developmental  his- 
tory is  more  condensed.  The  velum  of  the  embryo  is  want- 
ing or  exists  in  a  very  rudimentary  state.  The  mantle  and 
shell  are  developed  very  early.  The 
young  live  within  the  parent  fastened  to 
each  other  by  their  byssus.  The  shell 
(Fig.  178)  differs  remarkably  from  that  of 
the  adult,  being  broader  than  long,  trian- 
gular, the  apex  or  outer  edge  of  the  shell 
Fig.  i78^Yotmg  Unio.  no°ked,  while  from  different  points  within 
—After  Morse.  project  a  few  large,  long  spines.  So  dif- 
ferent are  these  young  from  the  parent  that  they  were  sup- 
posed to  be  parasites,  and  were  described  under  the  name  of 
GlocMdium  parasiticum.  They  are  found  in  the  parent 
mussel  during  July  and  August. 

The  ship-worm  (Teredo  navalis  Linn.  Fig.  179)  after  the 


DEVELOPMENT  OF  THE  SHIP- WORM. 


255 


segmentation  of  the  yolk  (Fig.  180  A)  passes  through  a 
veliger  stage,  the  shell  begins  to  grow,  and  when  five  days 


Pig.  179. — The  Ship-worm,    t,  siphons  ;  p,  pallets  ;  c,  collar  ;  s,  shell  ;  f,  foot. — 
After  Verrill. 

and  a  half  old  the  germ  appears  as  in  Fig.  178,  B,  the  shell 
almost  covering  the  larva.  Soon  after  this  the  velum 
becomes  larger,  and  then  decreases,  the  gills  arise,  the  audi- 
tory sacs  develop,  the  foot  grows,  though  not  reaching  to  the 
edge  of  the  shell,  and  the  larva  can  still  swim  about  free  in 
the  water.  When  of  the 
size  of  a  grain  of  millet, 
it  becomes  spherical,  as 
in  Fig.  180,  (7,  brown 
and  opaque.  The  long 
and  slender  foot  projects 
far  out  of  the  shell,  and 
the  velum  assumes  the 
form  of  a  swollen  ring  on 
which  is  a  double  crown 

of    cilia.        The    ears    and       Fig.  ISO.— Development  of   the  Ship-worm. 

eyes  develop  more,  and  ^«2^^SSW^Y%S 
the  animal  alternately  ^SSS^SS^Sff^' foot  ^  and  velum 
swims  with  its  velum,  or 

walks  by  means  of  the  foot.  At  this  stage  Quatre- 
fages  thinks  it  seeks  the  piles  of  wharves  and  floating 
wood,  into  which  it  bores  and  completes  its  metamor- 
phosis. On  the  coast  of  New  England  the  ship-worm 
lays  eggs  in  May  and  probably  through  the  summer. 


256  ZOOLOGY. 

Indeed  most  mollusks  spawn  in  the  summer.      Species  of 
Kellia,  Galeomma,  and  Montacuta  are  viviparous. 

Some  bivalves  get  their  growth  in  a  single  year.  The  fresh- 
water muscles  live  from  ten  to  twelve  years  and  perhaps 
longer ;  while  Tridacna  gigantea  probably  lives  from  sixty 
years  to  a  century.  Of  about  14,000  known  species  of 
Lamellibranchs,  from  8000  to  9000  are  fossil. 


CLASS  I.—  LAMELLIBRANCHIATA. 

Bilaterally  symmetrical  mollusks,  with  two  valves  lined  by  the  mantle,  con- 
nected by  a  dorsal  hinge  and  ligament;  no  head;  mouth  unarmed,  with 
two  pairs  of  labial  palpi;  intestine  coiled  in  the  visceral  mass,  usually 
passing  through  the  ventricle,  and  always  ending  at  the  posterior,  usually 
siphon-bearing,  end  of  the  body.  Foot  small,  sometimes  nearly  wanting, 
never  used  as  a  creeping  disk.  Usually  two  pairs  of  large  leaf -like  gills  on 
each  side  of  the  visceral  mass.  Sexes  usually  in  separate  individuals. 
Embryo  passing  through  a  so-called  morula,  gastrula,  and  free-swimming 
veliger  condition. 

Order  1.  Asiphonia. — Body-wall  or  mantle  without  siphons.  Shell 
sometimes  inequivalve.  (Ostrea,  Anomia,  Pecten,  Melea- 
grina,  Mytilus,  Area,  Trigonia,  Unio,  and  Anodonta.) 

Order  2.  Siphoniata. — Siphons  present.  Shell  equivalve.  (Chama 
Tridacna,  Cardium,  Venus,  Mactra,  Tellina,  Solen,  Clava- 
gella,  Aspergillum.) 

Laboratory  Work. — In  dissecting  the  clam,  etc.,  the  work  should  be 
performed  under  water,  in  a  dissecting  trough.  One  shell  should  be 
removed  by  cutting  the  adductor  by  a  pointed  scalpel,  the  mantle  dis- 
sected off  and  thrown  aside,  so  as  to  expose  the  gills,  heart,  and  kid- 
neys. In  dissecting  the  nervous  system  it  is  well  to  introduce  a  probe 
into  the  mouth,  and  then  cut  down  towards  it  from  above,  when  the 
white  supraoesophageal  ganglia  or  "brain"  will  be  found,  and  the 
other  ganglia  can  thence  he  traced  by  the  commissures  leading  from  the 
"  brain."  To  find  the  pedal  ganglia  and  otocyst,  cut  the  foot  vertically 
in  two.  The  heart  can  be  readily  found,  and  the  large  vein  at  the  base 
of  the  gills,  but  the  arterial  and  venous  systems  can  only  well  be 
studied  after  making  careful  injections.  For  ordinary  or  even  quite 
fine  injections,  Sabatier  used  a  mixture  of  lard  and  turpentine,  some- 
times adding  a  little  suet  or  wax  to  thicken  the  paste,  which  was 
colored  chrome  yellow,  vermilion,  or  blue.  For  histological  exami- 
nation he  used  essence  of  turpentine,  colored  as  before,  or  gelatine 


8CAPHOPOl)A.  SSf 

colored  by  carminate  or  ammonia,  or  Prussian  blue  dissolved  in  oxalic 
acid,  or  the  precipitate  of  cliromate  of  lead,  or  he  even  injected  air 
into  the  vascular  cavities.  The  mollusk  should,  before  injection,  be 
allowed  to  slowly  die  for  several  days,  and  the  fluids  to  leave  the  body. 
The  injection  should  be  made  before  decomposition  has  set  in,  otherwise 
the  vessels  will  burst.  Some  anatomists  plunge  mollusks  into  water 
to  which  has  been  added  alcohol  and  chlorhydric  acid.  After  remaining 
in  this  fluid  for  a  day  or  two  they  can  be  injected.  The  arterial  system 
can  best  be  injected  by  the  aortic  bulb,  or  aorta ;  the  venous  system 
may  be  filled  from  the  foot  through  the  aquiferous  orifice,  by  the 
adductor  muscle,  or  by  any  of  the  large  veins.  After  injection  the 
animal  should  be  plunged  into  cold  water  to  hasten  solidification  and 
then  placed  permanently  in  alcohol. 


CLASS  II. — CEPHALOPHORA  (Wlielks,  Snails,  etc.). 

General  Characters  of  Cephalophores. — We  now  come  to 
Mollusca  with  a  head,  distinguishable  from  the  rest  of  the 
body,  bearing  eyes  and  tentacles  ;  but  the  bilateral  symmetry 
of  the  body,  so  well  marked  in  the  Acephala,  etc.,  is  now 
in  part  lost,  the  animal  living  in  a  spiral  shell ;  still  the  foot 
and  head  are  alike  on  both  sides  of  the  body ;  while  the 
foot  forms  a  large  creeping  flat  disk  by  which  the  snail  glides 
over  the  surface.  Moreover,  these  mollusks  have,  besides 
two  pharyngeal  teeth,  a  lingual  ribbon  or  odontophore.  In 
a  shelless  land-snail  ( Onchidium)  Semper  has  discovered  the 
existence  of  dorsal  eyes,  constructed,  as  he  claims,  on  the 
Vertebrate  type.  They  are  in  the  form  of  little  black  dots 
scattered  over  the  back  of  the  creature,  and  their  nerves 
arise  from  the  visceral  ganglion.  Familiar  examples  of  the 
Cephalophora  are  the  sea -snails,  the  sea -slugs,  and  the 
genuine  air-breathing  snails  and  slugs. 

Order  1.  Scaphopoda. — A  very  aberrant  type  of  the  class 
is  Dentalium,  the  tooth  snail,  common  in  the  ocean  from 
ten  to  forty  fathoms  deep,  on  our  coast.  It  lives  in  a  long 
slender  tooth-like  shell,  open  at  both  ends,  while  the  animal 
has  no  head,  eyes,  or  heart,  and  the  foot  is  trilobed.  Owing 
to  the  presence  of  a  lingual  ribbon,  we  would  retain  it  in  the 
present  class,  though  it  is  a  connecting  link  between  this  and 


258 


ZOOLOGY. 


the  preceding  class,  and  is,  by  some  authors,  regarded  as 
the  type  of  a  separate  class  (Scaphopoda).     The  sexes  of 


Fig.  181.—  Development  of  Dentallum.  A,  morula  ;  B,  trochosphere  ;  C,  annu- 
lated  larva  ;  D,  larva  with  its  rudimentary  shell  ;  z,  velum  ;  a,  shell  ;  E,  young  much 
farther  advanced,  the  shell  or  body  segmented  ;  d,  rudimentary  tentacles  ;  .;,  sub- 
oesophageal  nerve-ganglia  ;  //",  digestive  canal,  and  liver  (/')  ;  the  foot  protrudes 
from  the  shell.  All  magnified.—  After  Lacaze-Duthiers. 

Dentalium  are  distinct.  The  young  is  a  trochosphere  and 
afterwards  becomes  segmented,  and  the  univalve 
shell  then  appears.  (Fig.  182.) 

Order  2.  Pteropoda.  —  In  these  winged-snails 
the  head  is  slightly  indicated  and  the  eyes  are 
rudimentary  ;  while  they  are  easily  recognized  by 
the  large  wing-like  appendages  (epipodium),  jne 
on  each  side  of  the  head.  The  shell  is  conical 
or  helix-like.  The  species  are  hermaphroditic. 
Cavolina  tridentata  Lamarck  and  Styliola  vitrea 
Verrill  (Fig.  183)  are  pelagic  forms,  occurring  on 
seas,  and  are  occasionally  taken  with  the 


SSu  nSneey  -  tow-net  off  tne  southern  coast  of  New  England. 
After  steams'.  Limaciua  arctica  Fabr.  is  of  the  size  of,  and 
looks  like,  a  sweet  pea,  moving  up  and  down  in  the  water. 
It  is  common  from  Labrador  to  the  polar  regions. 


PTEROPODA.  259 

A  common  form,  occurring  at  the  surface  in  harbors 
north  of  Cape  Cod,  as  well  as  many  miles  oif  shore,  is  Spiri- 
alis  Gouldii  Stimpson,  the  shell  of  which 
resembles  a  conical  Helix.  The  largest 
form  on  the  eastern  coast  of  North 
America,  extending  from  New  York  to  the 
polar  seas,  is  the  beautiful  Clione  papillon- 
acea  of  Pallas,  which  has  a  head  and  lin- 
gual ribbon.  It  is  rare  on  the  coast  of 
New  England,  but  abundant  from  Labra- 
dor northward.  We  haye  observed  it 
rising  and  falling  in  the  water  between 
the  floe-ice  on  the  coast  of  Labrador.  It 
is  an  inch  long,  the  body  fleshy,  with  no 
shell,  the  wings  being  rather  small. 

The  larvae  of  the  Pteropods  pass  through 
a  trochosphere  stage,  being,  as  in  Cavolina, 
spherical,  with  a  ciliated  crown.     It  after- 
wards assumes  a  veliger  form.     Fig.  184  represents  a  worm- 
like,  segmented,    Pteropod  larva,    the   adult   of   which   is 
unknown.     In  other  genera  the  larvae  are  annulated,  resem- 
bling the  larvae  of  Annelides. 

The  Pteropods  are,  in  some  degree,  a  generalized  type. 
They  have  a  wide  geographical  distribution  and 
a  high  antiquity ;  forms  like  Cavolina,  viz. : 
Theca,  Conularia,  Tentaculites,  Cornulites, 
etc.,  dating  back  to  the  palaeozoic  formation  ; 
Theca-like  forms  (Pugiunculus  and  Hyolithes) 
occurring  in  the  primordial  rocks. 

Order  3.  Gastropoda. — This  great  assemblage 
of  mollusks  is  represented  by  the  sea-slugs, 
limpets,  whelks   (Figs.   185-188),   snails,  and 
Fig.  m-ptero-  slugs.     The  head  is  quite  distinct,  bearing  one, 

pod  larva.  .      ,  i      -,       -,          >, 

and  sometimes,  as  in  the  land-snails,  two  pairs 
of  tentacles,  with  eyes  either  at  the  bases,  or  at  the  ends  of 
the  tentacles,  or,  as  in  Trivia  californica  (Fig.  189),  they 
are  situated  on  projections  near  the  base  of  the  tentacles. 
All  the  Gastropods  move  or  glide  over  the  surface  by  the 
broad  creeping-disk,  a  modification  of  the  foot  of  the  clam, 


260  ZOOLOGY. 

etc.     The  head  is  alike  on  each  side,  but  posteriorly  the  body 


FIG.  185. 


FIG.  186. 


FIG.  187. 


FIG.  188. 


Fig.  185.— A  Whelk.    Buccinum  cretaceum.    Labrador 
Fie;.  186.— A  Whelk.    Buccinum  ciliatum—  After  Morse. 
Fig.  187.—Strom!w8  pugilis.    West  Indies.— From  Tenney'e  Zoology. 
Fig.  188.— Pelican's  Foot.     Aporrhais  occidentals.     Northern  New  England.- 
After  Morse. 


ANATOMY  OF  THE  SNAIL. 


261 


is,  in  those  species  inhabiting  a  spiral  shell,  asymmetrical 
and  wound  in  a  spiral,  the  visceral  mass  extending  into  the 
apex  of  the  shell.  In  the  Nudibranchs  (Figs.  195,  197),  and 
the  slug,  the  body  being  naked  is  symmetrical 
on  each  side. 

The  digestive  tract  is  doubled  on  itself,  the 
vent  ending  on  one  side  of  the  mouth.  In 
some  Nudibranchs  the  intestine  has  numerous 
lateral  offshoots,  or  gastro-hepatic  branches, 
which  resemble  similar  structures  in  the  Plana- 
rian  and  Trematode  worms.  A  heart  is  always 
present,  except  in  the  parasitic  Entoconcha, 
and  sometimes,  as  in  Chiton,  Neritina,  and 
Haliotis,  it  is  perforated  by  the  intestine.  In 
some  genera  there  are  two  auricles  to  the  heart, 
but  as  a  rule  but  one  is  present.  The  Gastro- 
pods  breathe  by  gills  either  free,  or  contained 
in  a  cavity  in  the  mantle,  while  in  the  land- 
snails  (Pulmonata)  the  air  is  breathed  directly  by  a  lung-like 
gill  in  a  mantle-cavity.  The  kidney  is  single.  The  sexes 
are  either  distinct  or  united  in  the  same  individual. 

An  excellent  idea  of  the  structure  of  a  typical  Gastropod 
may  be  obtained  by  a  dissection  of  Natica  (Lunatia)  heros. 
This  is  a  large  mollusk,  common  between  tide-marks  from 
Labrador  to  Georgia.  On  taking  it  up  the  student  will 
notice  the  large,  round,  swollen,  porous  foot,  from  which 
the  water  pours  as  if  from  the  "rose"  of  a  watering-pot. 
The  shell  is  large,  composed  of  several  whorls,  with  a  small 
flattened  spire  or  apex.  The  aperture  is  large,  lunate  in 
shape,  and  can  be  closed  by  a  large  horny  door  or  oper- 
culum.  (In  some  mollusks,  Natica,  Turbo,  etc.,  the  oper- 
culum  is  of  solid  limestone,  and  small  ones  are  used  as  "  eye- 
stones,"  being  inserted  in  the  eye  and  moved  about  by  the 
action  of  the  lids,  thus  cleansing  the  eye  of  irritant  particles 
of  dust,  etc.) 

The  animal  should  then  be  placed  in  a  dish  of  salt  water, 
and  its  movements  observed.  There  are  but  two  short, 
broad,  flattened  tentacles,  situated  on  a  flap  or  head-lobe 
(prosoma)  of  the  mantle  or  body-walls.  No  eyes  are  present 


'  ZOOLOGY. 

in  this  species.  The  mouth  is  situated  in  front  of  the  foot 
and  at  the  base  of  the  head-lobe,  and  is  bounded  by  large  puck- 
ered swollen  lips.  Cutting  down  from  between,  the  tentacles. 
a  large  buccal  mass,  the  pharynx,  is  exposed.  The  mouth- 
caviry  is  roofed  with  two  broad  quadrant-shaped,  flat  thin 
teeth,  with  the  free-edge  serrated.  On  the  floor  of  the 
mouth  lies  the  "tongue/"5  or  lingual  ribbon  (Odontophore), 
which  is  folded  once  on  itself,  and  is  a  thin  band  composed 
of  eeren  rows  of  teeth,  those  forming  the  two  outer  rows 
long  and  much  curved,  those  of  the  central  row  being  stout 
and  three-toothed.  The  long  slender  oesophagus  is  tied 
down,  near  its  middle,  by  the  brain  (supraoBsophageal  gan- 
glion); just  behind  and  beneath  which  are  the  two  large 
salivary  glands.  The  oesophagus  suddenly  dilates  into  a 
large  stomach-like  pouch,  which  is  much  larger  in  this 
species  than  in  other  forms  allied  to  it.  It  is  a  sort  of  crop 
or  proTentriculus  (the  organ  of  Belle  Chiaje),  and  rarely  oc- 
curs in  the  Gastropods.  On  laying  it  open,  it  may  be  seen 
to  be  spongy  at  its  anterior  end,  and  posteriorly  divided  by 
numerous  transverse  partitions  into. small  cavities.  The 
oesophagus  beyond  it  is  again  slender,  and  leads  to  the 
stomach  situated  in  the  apex  of  the  shell,  partly  embedded 
in  the  liver-mass  which  lies  mainly  beyond  it.  From 
the  stomach  the  intestine  returns  to  the  head,  widely  dilat- 
ing into  a  large  saccnlated  cloaca,  before  the  free  up- 
turned vent,  which  is  situated  on  the  right  side  behind  and 
to  the  right  of  the  right  tentacle.  The  nervous  system  is 
represented  by  a  pair  of  large  ganglia,  forming  the  brain 
(supraoesophageal  ganglia)  situated  just  below  and  behind 
the  pharynx.  The  two  other  ganglia  were  not  traced,  but  as 
a  rule  in  all  Cephalophora  there  are  three  pairs  of  ganglia, 
i.  £.,  the  brain  (supraoesophageal  ganglia)  with  commissures 
passing  around  the  gullet  to  the  pedal  or  infraoesophageal 
ganglia,  thus  forming  the  oesophageal  nervous  ring,  while  the 
visceral  or  parieto-splanchnic  ganglia  are  placed  at  a  varying 
distance  behind  the  head. 

The  heart,  contained  in  its  pericardia!  sac,  and  consisting  of 
a  ventricle  and  auricle,  is  situated  near  the  posterior  end  of 
the  gills.  The  latter  are  disclosed  by  laying  aside  the  man- 


DEVELOPMENT  OP  GASTROPODS. 


tie  on  the  left  side  of  the  body  behind  the  head.  In  a  large 
Lunatia  it  is  an  inch  long,  with  a  vein  at  the  base,  the  gill- 
lobes  arranged  like  the  teeth  in  a  comb.  A  smaller,  much 
narrower  gill  lies  within  and  parallel  to  it.  The  ovary  is 
situated  near  the  stomach,  the  ovi- 
duct  ending  near  the  vent. 

The  eggs  are  laid  in  capsules  (Kg. 
190,  Purpura  lapittus  and  two  egg- 
capsules)  of  yaried  form  attached 
to  rocks  or,  as  in  Trochus  and  the 
Xndibranchs,  in  masses  of  jelly  at- 
tached to  sea-weeds  or  stones. 

As  a  type  of  the  mode  of  devel- 
opment of  Gastropods  may  be  cited  that  of  Calyptrcta  si- 
nensis,  represented  in  our  waters  by  Calyptraa  striata  Say 
(Fig.  191). 


According  to  Salensky,  after  segmentation  of  the  yolk 
into  eight  cells  the  first  four  cells  or  "spheres  of  segmenta- 
tion" subdivide,  enclosing  the  yolk-mass,  and  constituting 
the  ectoderm  or  outer  germ-layer,  the  yolk-mass  forming  the 
endoderm.  The  cells  of  the  outer  germ-layer  multiply  and 
form  the  blastoderm,  from  which  the  skin,  mantle,  and  ex- 
ternal organs,  as  well  as  the  walk  of  the  mouth,  arise.  The 
mouth  of  the  gastrnla  is  formed  by  the  invagi- 


264  ZOOLOGY. 

nation  of  the  outer  germ-layer  ;  the  sides  of  the  primitive 
mouth  form  the  two  sails  of  the  velum  or  swimming  organ, 
and  the  embryo  now  assumes  the  veliger  stage  (Fig.  192). 
Soon  the  middle  germ-layer  (mesoderm)  arises,  and  from 
the  cells  composing  it  are  developed  the  muscles  of  the  foot 
and  head,  as  well  as  the  heart  itself.  The  mantle  or  body- 
wall  next  develops,  and  from  it  the  shell,  which  originates  in 
a  cup-like  cavity  which  is  connected  only  around  the  edge 
with  the  mantle,  being  free  in  the  centre.  The  eyes  and  ears, 
or  otocysts,  next  appear,  both  organs  arising  as  an  infolding 
of  the  outer  germ-layer.  Hitherto  symmetrical,  the  alimen- 
tary canal  now  begins  to  curve  to  the  left,  and  the  visceral 
sac,  or  posterior  part  of  the  embryo  hangs  over  on  one  side. 
The  nervous  system  is  the  last  to  be  developed. 

Fig.  193  represents  the  asymmetrical  larva  with  the  shell 
enveloping  a  large  part  of  the  body,  and  the  ciliated  velum 
(v)  and  foot  (/)  well  developed.  A  temporary  larval  heart 
(h)  assumes  quite  a  different  position  from  the  heart  of  the 
adult,  and  the  primitive,  deciduous  kidney  (k)  is  situated  in 
quite  a  different  place  from  the  permanent  kidney.  The 
further  changes  consist  in  a  gradual  development  of  the  hel- 
met-like shell,  the  disappearance  of  the  temporary  larval 
structures,  and  the  perfection  of  the  organs  of  adult  life,  the 
gills  appearing  quite  late. 

The  development  of  Trochus,  the  top-shell,  exhibits  more 

strikingly  the  trochosphere  and 
veliger  stages  of  molluscan  life, 
and  most  Gastropods  develop 
like  this  form.  The  velum 
at  first  forms  a  ciliated  ring 
(Fig,  194,  A,  v)  on  the  front  end 
of  the  trochosphere.  Fig.  194, 
B}  represents  the  veliger  state. 
It  thus  appears  that  the  tem- 

Fig.  194.— Larval   Trochus.     A,  tro-  -.  -f  T  £  £ 

chosphere ;  v,  velum ;  B,  veifeer  state  •  porary  larval  or  veliger  lorm  or 
saiemnskyh;  f>  *  ^'-ASt<*  the  Gastropods  are  of  vermian 

origin,  the  organs  last  to  be  de- 
veloped, i.  e.,  the  foot,  shell  and  lingual  ribbon,  which  are  the 
distinctively  molluscan  characters,  being  the  last  to  appear. 


NUDIBRAXCH  MOLLUSKS. 


265 


The  Nudibranch  mollusks,  such  as  the  Eolis  and  Doris  and 
allied  forms,  breathe  by  external  gills,  arranged  in  bunches 
on  the  back,  as  seen  in  Fig.  195,  jffiolis  (Mon- 
tagua)  pilata  (Gould),  a  common  species  on 
the  coast  of  New  England.  In  Doris  (Fig. 
197),  they  are  confined  to  a  circle  of  pinnate 
gills  on  the  hinder  part  of  the  back.  They  are 


FIG. 195. 


FIG.  196. 


FIG.  197. 


Fig.  195.-^EWw,a  Nndibranch. 

Fig.  19G.  —  Veliger  of  Tergipes.    v,  velum  ;  s,  shell ;  d,  foot ;  i,  otocysts.— After 
Schultze. 
Fig.  \yi.-Darl8  bilamellata.    New  England  coast. 

shelless,  and  not  uncommon  just  below  low-water  mark, 
laying  their  eggs  in  jelly-like  masses  coiled  up  on  stones  and 
the  surface  of  sea-weeds.  Though  the  adults  are  shelless, 
the  embryos  at  first  have  a  shell 
(Fig.  196,  s),  indicating  that 
the  Nudibranchs  have  descend- 
ed from  shelled  Gastropods. 
Fig.  196  represents  the  veil-  ^  m_P^m  ^erostropha.  com- 

ger      Of       Tergipes      ladnulata    mon  pond-enail.— After  Morse. 

Schultze,  allied  to  Doris,  with  its  large  ciliated  velum,  and 
protected  by  a  deciduous  shell,  which  finally  disappears  with 
the  velum. 

The  air-breathing  mollusks,  Pulmonata,  are  represented  by 
the  pond-snails,  Pliysa  (Fig.  198)  and  LimncBus  (Figs.  199, 
200),  and  the  land-snails  and  slugs.  Fig.  205  represents  a 
slug  suspended  by  a  mucous  thread  from  a  twig. 

The  common  snail,  Helix  albolabris  Say,  is  a  type  of  the 
air-breathing  mollusks.  Fig.  201  represents  this  snail  of 
natural  size,  in  its  shell.  The  opening  to  the  lung  is  seen 
at  #,  and  at  B  is  represented  the  heart  and  lung  of  the  gar- 
den slug  (Limax  flavus).  Fig.  202  represents  Helix  albo- 
labris  with  the  shell  removed,  and  the  mantle  thrown  buck, 


266 


ZOOLOGY. 


showing  the  lung  and  heart  (h)  and  the  mouth  (m)  as  well 
as  the  four  tentacles,  with  an  eye  at  the  end  of  the  two 
upper  tentacles.  Fig.  203  shows  the 
brain  and  pedal  ganglia  of  Helix  albola- 
bris.  The  tentacles  when  carefully  exam- 
ined may  be  found  to  contain  both  the 
eyes  (e)  with  the  optic  nerve  (op)  and  the 
olfactory  nerve  (Fig.  206,  o).  Fig.  204 
represents  the  jaw  and  lingual  ribbon  of 
Helix. 

The  eggs  of  the  pond-snails  are  laid  in 
transparent  capsules  attached  to  sub- 
merged leaves,  etc.  Those  of  Pliysa 
lieterostropha  are  laid  in  the  early  spring, 
and  three  or  four  weeks  later  from  fifty  to 
sixty  embryos  with  well-formed  shells  may 
Fig.i99.— Limncewap-  be  found  in  the  capsule. 

The  eggs  of  Limnaus  are  laid  late  in 
the  spring  in  capsules  containing  one  or  two  eggs,  and  sur- 
rounded by  a  mass  of  jelly.  After  passing  through  the  mo- 


Fig.  ^OO.—Limnceus  elodes,  a  common  pond-snail,  showing  its  variations. — 
After  Morse. 

rula,  gastrula,  and  trochosphere  stages  a  definite  veliger 
stage  is  finally  attained.  The  foot  is  large  and  bilobed,  the 
mantle  and  shell  then  arise,  and  the  definite  molluscan  char- 
acters are  assumed,  the  shell,  creeping  foot,  mantle-flap,  eyes, 
and  tentacles  appearing,  and  the  snail  hatching  in  about 
twenty  days  after  development  begins. 

Land-snails  and  slugs  lay  their  eggs  loose  under  damp 
leaves  and  stones,  and  development  is  direct,  the  young 
snail  hatching  in  the  form  of  the  adult. 


,  HELIX  ALBOLABRIS. 


367 


FIG.  203. 


FIG.  204. 


Fig.  201.—  Helix  albolahins,  natural  pize.    a,  orifice  of  lung.    Also  the  heart  and 
ung  of  Limax  Jtatntt,  magnified. 

•  Fig.  202.— Helix  albolabris,  with  the  shell  removed  to  show  the  heart  (/ )  and  the 
Ting  ;  m,  mouth.— This  and  Figs.  201-204  after  Leidy. 

Fig.  203. — Nerve-centres  of  Helix  albolaJbris. 

Fig.  204.— Jaw  (lower  figure)  and  side  and  top  view  of  teeth  of  lingual  ribbon  of 
Helix  albolabris. 


268 


ZOOLOGY 


The  group  of  mollusks  represented  by  Chiton  (Fig.  207, 
Chiton  ruler)  have  been  referred  to  the  worms  by  Jhering, 
on  account  of  the  segmented  appearance 
of  the  plated  shell,  and  the  nervous  sys- 
tem,   which    consists    of     two    parallel 
cords,    connected    by    several    commis- 
sures ;  *  as  well  as  from  the  fact  that  the 
intestine  ends  at  the  hinder  end  of  the 
body.     The  young 
is  oval  when  hatch- 
ed, and  is  a  trocho- 
spheie,    having    a 
ciliated  ring  in  the 
Fig.  205.-siug.  Nat-   middle  of  the  body 
with  a  long  tuft  of 
large  cilia  on  the  head.     Afterwards 
it  becomes  segmented,  as  in  Fig.  208, 
and  is  remarkably   worm -like,   the 
limestone  plates  of  the  adult  corre- 
sponding to  the  primitive  larval  rings. 
Certain  Gastropods  are  useful  either 
as  food  or  in  the  arts.     In  Europe 

•f  . . ,      .        TII  IT      i •  i   /  T-»    i  1 1          Fie.  206. — End   of    tentacle 

Littorina  httorea,  the  limpet  (Patella  Of  a  snail.  «,  eye ;  op,  optic 
vulgata),  the  whelk  (Buccinum  un-  nerve;  °' olf actory  nen 

datum),  and  the  Roman  snail  (Helix 
pomatia)  are  eaten.  The  sea -ear 
(Haliotis)  is  roasted  in  the  shell. 
The  animal  of  Cymba,  Stromlus  gi- 
gas,  Turlo,  Trochus,  and  Conus  are 
eaten  in  the  tropics,  while  many  of 
the  larger  forms  are  used  for  fish- 
bait.  Pearls  are  sometimes  found  in 
the  species  of  Haliotis  arud  Turbo. 
The  beautiful  shell  of  Cassis  is  made 
into  cameo  pins,  and  the  shell  of 
Strombus  gigas  is  in  the  West  Indies  made  into  ornaments. 

*  In  Fissurella  and  ffaliotis  the  two  nerve-cords  from  the  pedal  gan- 
glia are  also  united  by  nine  transverse  commissures,  so  that  here  also 
we  have  an  approach  to  the  double  ganglionated  cord  of  worms. 


FIG.  207. 

Pia.  208. 

Fig.  207—  Chiton  ruber. 
Fig.  208.  —Segmented  larva 
of  CTiiton. 


FOSSIL  GASTROPODS. 


269 


Various  shells,  such  as  Marginella,  TurUnella,  etc.,  are 
strung  in  bracelets  and  armlets  by  savages.  Cyprcea  moneta, 
the  cowry  (Fig.  209),  is  used  for  money,  and  other  shells 
are  worked  into  various  shapes  for  wampum  or  aboriginal 
money.  Fig.  210  represents  an  Olivella,  used  by  the  Cal- 
ifornian  Indians  as  money.  Murex  and  Purpura  afford 
the  Tyrian  dye. 

While  a  few  Gastropods  are  pelagic,  living  upon  the  high 
seas,  such  as  lanthina  and  the  Nudibranch  Glaucus,  most 
of  the  species  are  submarine  and  live  in  all  seas  ;  the  hardier, 
most  widely  diffused  species  living  between  tide-marks,  the 
more  delicate  forms  in  deep  water,  ranging  from  low-water 


Pro.  209.  FIG.  210. 

FIG.  209.— Cyprcea  moneta.— After  Stearns. 
FIG.  SlO.—Ohvella  biplicata.-A.fter  Stearns. 

mark  to  fifty  or  one  hundred  fathoms.  The  abyssal  fauna  at 
the  depth  of  from  500  to  about  2000  fathoms  has  a  few  char- 
acteristic mollusks.  Many  live  on  land  and  in  fresh  water. 
The  largest,  most  highly  colored  shells  live  in  the  tropics, 
while  those  found  in  the  temperate  zones  are  less  beautiful, 
and  the  arctic  species  are  the  smallest  and  dullest  in  color. 
The  shells  of  .the  eastern  coast  of  North  America  are 
divided  into  several  assemblages,  or  faunae,  the  West  Indian 
or  tropical  shells,  in  some  cases,  reaching  as  far  north  as 
Cape  Hatteras ;  between  this  point  and  Cape  Cod  a  north 
temperate  assemblage  occurs,  and  north  of  Cape  Cod  the 
molluscan  fauna  is  essentially  Arctic ;  many  species  being 
common  to  the  arctic  and  subarctic  seas  of  the  circumpolar 
regions. 


270  ZOOLOGY. 

Marine  shells  in  time  date  back  to  the  lowest  Silurian 
period ;  such  are  Maclurea,  Holopea,  Murchisonia,  Pleuro- 
tomaria,  etc.,  which  occur  fossil  in  rocks  of  the  Potsdam 
period.  The  Palaeozoic  Gastropods  are  few  in  number  com- 
pared with  those  occurring  in  Cretaceous  and  especially  Ter- 
tiary formations. 

The  earliest  land-snails  occurred  in  the  Coal  Period ;  the 
living  species  are  exceedingly  numerous,  and  often  much  re- 
stricted in  range,  especially  in  the  tropics ;  the  arctic  forms 
are  very  scarce,  but  four  or  five  species  occurring  in  Green- 
land. There  are  over  22,000  species  of  Cephalophora  known, 
of  which  7000  are  fossil.  There  are  6500  species  of  Pulmo- 
nata. 

Subclass  4.  Heteropoda. — The  Heteropods  form  a  distinct 
subclass,  the  systematic  position  of  which  was  for  a  long 
time  unsettled ;  but  they  are  now  classed  among  the  Gas- 
tropods, being  in  fact  related  to  the  Opistliobranchiata. 
Their  most  striking  peculiarity  is  the  form  of  their  foot, 
the  anterior  and  middle  portions  of  which  are  expanded  to 
form  a  leaf-like  fin,  which  often  bears  a  sucker  ;  the  pos- 
terior part  of  the  foot  is  much  elongated,  and,  reaching  far 
backwards,  appears  to  form  a  tail-like  continuation  of  the 
body.  The  Heteropods  are  more  or  less  transparent,  and 
are  found  swimming  upon  the  surface  of  the  ocean,  upon 
their  backs  with  their  foot  upwards.  The  shell  may  or  may 
not  be  developed  ;  when  present  it  may  be  either  simple  or 
coiled.  The  nervous  system  resembles  closely  that  of  the 
true  Gastropods,  but  is  more  highly  developed;  the  brain 
consists  of  several  supraoesophageal  ganglia  forming  part  of 
an  oesophageal  ring.  From  the  brain  arise  the  optic  and 
auditory  nerves.  The  two  large  eyes  lie  in  special  capsules 
near  the  feelers,  and  are  movable  by  several  muscles.  The 
otocysts  are  also  large,  and  contain  a  large  spherical  otolith. 
The  otocysts  are  lined  by  an  epithelium  with  bundles  of 
long  vibratile  hairs,  and  with  a  cluster  of  sensory  cells,  form- 
ing a  macula  acustica.  Organs  of  touch  have  also  been 
described.  The  sensory  apparatus  of  the  Heteropods  are 
highly  specialized,  and  have  been  studied  by  Claus,  Boll, 
Flemming,  and  others.  The  odontophore  is  well  developed ; 


THE  HETEROPOD  MOLLUSKS.  271 

the  tongue  or  radula  has  highly  characteristic  teeth,  which 
serve  these  rapacious  animals  to  seize  their  prey.  The  in- 
testine runs  straight  back  from  the  mouth,  and  after  mak- 
ing one  or  two  coils  ends  in  the  vent.  The  excretory  organs 
open  near  the  anus;  the  contractile  tube  opens  internally 
into  the  pericardial  cavity,  and  resembles  in  form  and  posi- 
tion the  excretory  organ  of  the  Pteropoda.  The  circula- 
tion is  imperfect,  the  blood  passing  from  the  wide  sinuses 
of  the  body  to  the  ventricle  of  the  heart.  From  the  auricle 
springs  the  aorta,  which  subdivides  into  several  branches 
that  open  freely  into  the  body-cavity.  The  circulation  can  be 
easily  watched,  owing  to  the  transparency  of  the  body.  The 
aeration  of  the  blood  is  effected  partly  through  the  skin, 
partly  through  gills,  except  in  a  few  species.  The  branchiae 
are  either  thread-  or  leaf-like  ciliated  appendages,  which 
may  either  be  free  or  enclosed  in  the  mantle-cavity.  The 
sexes  are  distinct.  The  males  can  be  readily  recognized  by 
the  large  copulatory  organ,  which  hangs  free  on  the  right 
side  of  the  body.  The  sexual  glands  fill  the  posterior  por- 
tion of  the  visceral  cavity,  and  are  partly  imbedded  in  the 
liver.  The  oviduct  is  complicated  by  the  presence  of  an 
albumen  gland  and  a  receptaculum  seminis.  It  opens  on 
the  right  side  of  the  body. 

The  Heteropods  are  exclusively  marine,  but  are  found  in 
all  quarters  of  the  world.  The  number  of  species  is  small, 
and  there  are  two  orders  only — the  Pterotraclieidce  with  a 
small  or  no  shell  and  free  gills,  and  the  Atlantidce  with  a 
large  coiled  shell  and  gills  placed  in  the  mantle.  Ptero- 
trachea  (Firola)  coronata  Forsk.  is  found  in  the  Mediter- 
ranean, and  on  account  of  its  transparency  has  often  been 
investigated.  The  Heteropoda  live  together  in  large  num- 
bers, and  feed  on  small  animals. 

The  eggs  are  laid  in  cylindrical  strings,  which  soon  break 
up  into  numerous  pieces.  The  segmentation  of  the  yolk  is 
complete  but  irregular.  The  embryo  rotates  within  the  egg 
during  the  veliger  stage,  when  it  has  two  distinct  sails,  or 
lobes  of  the  velum,  and  a  ciliated  foot  with  an  operculum. 
In  this  form  it  leaves  the  egg.  The  velum  enlarges  and 
forms  several  divisions.  The  otocysts,  eyes,  and  tentacles  are 


272  ZOOLOGY. 

then  developed.  The  foot  gradually  lengthens  and  forms  the 
characteristic  fin  or  keel.  The  velum  is  meanwhile  ab- 
sorbed, the  operculum  (Carinaria),  or  the  operculum  and 
shell,  are  thrown  off,  and  the  larva  gradually  assumes  the 
form  and  organization  of  the  adult.  The  close  relationship 
of  the  Heteropods  and  Gastropods  is  shown  by  the  great 
similarity  of  their  larvae.  Gegenbaur  even  goes  so  far  as  to 
include  them  under  the  Opisthobranchiata,  while  von  Jher- 
ing  unites  them  with  Chitons  and  some  other  forms  under 
the  name  of  ArthrocoMidw ;  for  the  present  it  seems  best 
to  retain  them  as  a  subclass. 

The  fossil  genus  Bellerophon  is  closely  related  to  the 
Atlantidce. 

CLASS  II.— CEPHALOPHORA. 

Mottusks  with  a  distinct  head,  with  tentacles,  eyes  and  ears  in  the  head  ; 
the  foot  forming  a  creeping  disk;  the  body  either  naked  and  bilaterally  sym- 
metrical, or  enclosed  in  a  spiral  shell,  and  consequently  behind  the  head 
asymmetrical.  Mouth  with  pharyngeal  teeth  and  a  lingual  ribbon  (odon- 
tophore).  Nervous  system  consisting  of  four  pairs  of  ganglia,  the  brain 
well  developed.  The  intestine  usually  ending  near  the  mouth.  The  heart 
with  usually  a  single  auricle.  Breathing  by  a  single  gill,  or  a  lung-like 
gill ;  a  double  kidney,  but  forming  a  single  mass.  Sexes  united  or  sepa- 
rate. Young  passing  through  a  morula,  gastrula,  sometimes  a  trocho- 
sphere  and  usually  a  veliger  stage;  in  the  land-snails  development 
direct. 

Subclass  1.  Scaphopoda.—No  head,  several  long  thread-like  tentacles  ; 
foot  long,  trilobed.  Shell  long,  conical,  open  at  each  end. 
A  single  order  SolenoconchcB.  (Dentalium,  Siphonodenta- 
lium.) 

Subclass  2.  Pteropoda  —Body  with  two  wing-like  expansions  (velum) 
on  the  front  part  of  the  foot,  for  swimming  ;  body  naked  or 
shelled.  Hermaphroditic.  Larva  with  a  velum  and  shell. 
Order  1.  Thecostomata  (Hyalea,  Cleodora,  Cavolina).  Order 
2.  Oymnosomata.  (Clione). 

Subclass  3.  Gastropoda.—  Order  1.  Prosobranchiata  (Haliotis,  Patella, 
Trochus,  Littorina,  Lunatia,  Paludina,  Turritella,  lanthina, 
Cyprsea,  Strombus,  Cassis,  Buccinum,  Nassa,  Purpura.) 
Order  2.  Opisthobranchiata.  (Bulla,  Aplysia,  Eolis,  Doris.) 
Order  3.  Pulmonata.  (Limnaeus,  Planorbis,  Auricula,  Helix, 
Bulimus,  Limax). 


GENERAL  CHARACTERS  OF  CEPHALOPODS.   °73 

Subclass  4.  Heteropoda. — Naked  or  shell-bearing  mollusks,  with  a  large 
prominent  head,  large  movable  eyes,  and  foot  with  a  keel- 
like  fin.  The  sexes  are  distinct.  Respiration  by  gills.  Or- 
der 1.  Pterotracheida. — Pterotrachea,  Carinaria,  Firoloides. 
Order  2.  AtlantidcB.— Atlanta  (living) ;  Bellerophon  (fossil). 

Laboratory  Work. — The  Gastropods  are  very  difficult  to  dissect,  and 
it  is  quite  essential  that  the 
specimen  be  freshly  killed,  and 
that  it  has  died  as  fully  ex- 
panded as  possible.  For  this 
purpose  they  should  be  al- 
lowed, as  Verrill  suggests,  to 
die  in  stale  sea-water,  with 
the  parts  expanded  ;  when  the 
animal  is  nearly  dead,  the  soft 
parts  can  be  forcibly  held  out 
by  the  hand  while  the  animal 
is  killed  by  immersion  in  alco- 
hol. Shells  and  other  marine 
animals  may  be  obtained  by 
means  of  the  dredge  (Fig:. 
211),  an  iron  frame  with  a 

net,  to  which  is    attached  a  Fig.  211.— Dredge, 

rope  and  weight. 


CLASS  III. — CEPHALOPODA  (Squids  and  Cuttle-fishes). 

General  Characters  of  Cephalopoda.  —  The  essential 
features  of  this  class  may  be  observed!  by  a  study  of  the  com- 
mon squid,  represented  by  Pig.  212.  The  following  account 
is  based  on  dissections  of  Loligo  Pealii  Lesueur  (Fig. 
213),  A  general  view  of  the  body  of  the  entire  squid, 
with  its  arms  and  suckers,  is  given  in  the  accompanying 
illustration  (Fig.  212)  of  Loligo  pallida  Verrill.  The  body 
is  fish-like,  pointed  behind,  and  with  two  broad  fleshy  fin- 
like  expansions  at  the  end  of  the  body.  The  head  is  dis- 
tinct from  the  mantle  or  body,  and  the  mouth  is  surrounded 
by  a  crown  of  ten  long  stout  pointed  arms,  provided  on  the 
inner  side  with  two  rows  of  alternately  arranged  cup-shaped 
suckers,  each  sucker  being  spherical,  hollow,  with  a  horny 


2T4 


ZOOLOGY. 


rim  inside.  Two  of  the  ten  arms  arise  from  the  under  side 
of  the  head  ;  they  are  twice  the  length  of  the  eight  others, 
and  oval  at  the  end.  On  each  side  of  the  head  behind  the 
tentacles  are  the  remarkably  large  eyes,  which,  though  usual- 
ly said  to  be  more  like  the  vertebrate  eye  than  those  of  any 

other  invertebrate,  are  really 
constructed  fundamentally  on 
the  same  plan  as  the  eye  of 
the  snail ;  differing  in  several 
important  respects  from  that 
of  a  Vertebrate,  the  resem- 
blances between  the  two  being 
superficial,  while  the  struc- 
ture of  the  eyes  of  mollusks  is 
quite  unlike  that  of  Crusta- 
ceans, insects  or  Vertebrates. 
The  mantle  loosely  invests 
the  front  of  the  body  next  to 
the  head,  so  that  the  water 
passes  in  around  the  neck  in 
order  to  bathe  the  gills,  which 
are  quite  free  from  the  visce- 
ral mass.  The  mantle  is  beau- 
tifully colored  and  spotted, 
the  change  of  color  being  due 
to  the  change  in  f—^  ~e  the 
pigment  masses  or  cliromato- 
phores,  which  are  under  the 
influence  of  the  peripheral 
norves. 

The  mantle  is  supper 
;  male.  About  a  horny  4fpen"  :    '          •),  or 

terVerrill. 

pen-shaped  thin  suppori 
tending  from  the  upper  side  of  the  anterior  edge  < 
mantle  to  the  end  of  "W>  body.     In  the  Sepia  of  the  Medi- 
Sea  this  is  U4ek,  formed  of  limestone,  and  is 
called  the  "  cuttle-fish  bone  " 

Tho  organs  of  digest.  . 

oesophagus,  sir- 


Fig.  213.— 
one  third  natural  suse.^After Verrlll. 


pa 


FIG  213-Anatomy  of  common  squid.-Drawn  by  J.  S.  Kingsley,  from  the  author's 
dteaecttoiw.    The  brain  (d )  in  nature  is  situated  above  the  crsophagns. 


276  ZOOLOGY. 

between  the  tentacles,  and  is  surrounded  by  a  double  fleshy 
lip,  the  outer  fold  of  the  lip  bearing  short  fleshy  pointed  lobes 
opposite  the  spaces  between  the  tentacles.  The 
pharynx  is  large,  muscular  and  bulbous,  contain- 
ing two  powerful  horny  teeth,  shaped  like  a  par- 
rot's beak ;  the  two  jaws  are  unequal,  the  lower 
one  the  smaller,  moving  vertically.  On  opening 
the  base  of  the  smaller  jaw,  the  lingual  ribbon  or 
odontophore  (Fig.  213,  po)  may  be  discovered ;  it 
consists  of  seven  rows  of  teeth,  somewhat  as  in 
those  of  Architeuthis  Hartingii  (Fig.  215). 

The  oesophagus  (ce)  is  long  and  slender,  with  two 
long  oval  salivary  glands  (sg)  on  each  side  of  it,  just 
behind  the  pharynx;  the  salivary  duct  leading 
into  the  mouth-cavity.  The  oesophagus  has 
several  internal  longitudinal  folds,  and  passes 
on  one  side  of  the  large  liver  (I)  which  lies  in 
front  of  the  stomach,  and  which  is  about  one 
third  as  long  as  the  whole  body,  extending  back- 
wards. 

On  laying  open  the  stomach,  a  series  of  large 
semicircular  transverse  curved  valves  may  be 
Pig.  214.—  seen,  occupying  the  ^anterior  third  of_the^stom- 
Suida,  dSi  ach  (s),  while  beyond-  are  scattered  glandular 
?idz e  -After masses.  ^The  pyloric  end  opens  into  an  oval 
Verriii.  ccecum  (ca)  with  about  fourteen  longitudinal, 
thin  high  ridges.  There  is  no  spiral  portion  attached.  The 
intestine  (in)  is  straight,  thick,  and  passes  forward,  ending 
in  a  large  vent  (a),  the  edges  of 
which  are  lobulated.  The  "  ink- 
bag"  (Fig.  213,  t)  can  be  recog- 
nized as  a  purse-like  silvery  sac, 
filled  with  a  dense  pigment,  the 
sepia,  which,  like  the  Chinese  F'g-  215.— Part  of  lingual  ribbon  of 

r.  ,    .         -,  Architeuthis  Hartingii ;  enlarged. 

sepia,  can  be  used  for  drawing. 

The  duct  is  straight,  and  is  intimately  attached  to  the  in- 
testine, ending  close  to  the  vent,  both  the  vent  and  open- 
ing of  the  duct  of  the  ink-bag  being  situated  at  the  bot- 
tom of  the  funnel  or  siphon  (Fig.  213,  /),  which  is  a  large 


^  LOLIGO.  277 

^V.     -Oy»  ^' 

short  muscular  canal  with  a  large  orifice  extending  on 
the  ventral  side  to  the  base  of  the  tentacles.  Throughi  / 
this  siphon  passes  excrementitious  matter  as  well  as  the  ink, 
and  the  stream  of  water  which  is  forcibly  ejected  from  the 
siphon,  thus  propelling  the  squid  through  and  sometimes 
out  of  the  water. 

The  two  gills  (Fig.  213,  g),  are  large,  long  slender  bodies,  at- 
tached by  a  thin  membrane  to  the  inner  wall  of  the  mantle, 
and  are  quite  free  from  the  visceral  mass.  From  the  bran- 
chial vein  arise  two  rows  of  lamellse  like  the  teeth  of  a  comb. 
At  the  base  of  each^gill  is  a  flatted  oval  body,  the  "bran- 
chial heart,"  or  auricle  (Fig.  213,  bh).  The  auricles  are  quite 
separate  from  the  large  four-cornered  flat  ventricle  (Fig. 
213,  h),  lying  in  front  of  the  stomach,  and  which  throws  off  an 
artery  from  each  corner,  the  aorta  being  the  largest,  and 
passing  parallel  to  the  oesophagus,  while  a  large  vein  (vena 
cava)  is  sent  off  to  the  gills  from  a  circular  sinus  in  the 
head. 

The  nervous  system  is  more  complicated  than  usual  in 
Mollusca,  and  is  very  difficult  to  dissect.  In  Loligo  Pealii  the 
highly  concentrated  nervous  system  is  mainly  contained  in  an 
imperfect  cartilaginous  brain-box  (eg),  a  slight  anticipation  of  ~ 
the  skull  of  the  Vertebrates.  The  brain  (supracesophageal 
ganglion,  Fig.  213,  d)  rests  upon  the  very  large  optic  nerves, 
which  dilate  at  the  base  of  the  eye,  the  latter  being  partially 
imbedded  in  sockets  in  the  brain-box.  The  visceral  (parie- 
tosplanchnic)  ganglion  lies  beneath  and  a  little  behind  the 
brain,  supplying  the  nerves  for  the  ears  (otocysts),  which 
are  enclosed  in  the  cartilaginous  brain-box,  and  there  is  a  fine 
canal  leading  from  the  ears  to  the  surface  of  the  body,  so 
that,  as  Gegenbaur  states,  it  is  possible  to  distinguish  a  mem- 
branous and  a  cartilaginous  labyrinth,  analogous  to  the 
similar  parts  found  in  the  Vertebrates.  The  pedal  ganglion 
(Fig.  213,  p)  is  paired  with  the  visceral  ganglion  (Fig.  213,  ?»), 
but  lies  in  front  of  it,  behind  and  under  the  bulbous  pha- 
rynx, and  from  it  arise  ten  nerves  (t),  which  are  distributed  one 
to  each  arm,  passing  between  the  two  rows  of  suckers.  Two 
smaller  ganglia,  the  superior  buccal  and  inferior  buccal,  lie 
one  above  and  one  below  the  beginning  of  the  oesophagus. 


278 


ZOOLOGY. 


Besides  this  set  of  five  cephalic  ganglia,  there  are  three  pairs 
of  ganglia  belonging  to  the  visceral  or  sympathetic  nerve, 
which  arise  from  the  visceral  ganglion  situated  among  the 
viscera  ;  a  single  one  (the  ventricular  or  splanchnic  ganglion) 
is  situated  over  the  stomach  near  the  origin  of  the  aorta, 
which  sends  a  nerve  to  the  coecum,  and  another  accompanies 
the  aorta ;  the  mate  to  this  ganglion  is  situated  near  the 
vena  cava.  A  pair  of  ganglia  is  situated  on  the  mantle  walls 
(ganglia  stellata),  and  there  are  two  branchial 
ganglia.  The  kidneys  (&)  are  irregular 
branching  spongy  bodies,  in  intimate  con- 
nection with  the  auricles  or  branchial  hearts. 
The  sexes  are  distinct.  The  ovary  (o)  is 
large,  especially  when  the  eggs  are  ripe,  and 
is  situated  in  the  end  of  the  body-cavity. 
The  single  oviduct  is  as  in  some  worms, 
separate  from  the  ovary,  and  in  this  respect 
the  Cephalopods  approach  or  anticipate  the 
Vertebrates,  in  which  the  oviduct  is  also 
separate  from  the  ovary.  The  oviduct 
(ov)  is  a  thick  straight  tube,  with  a  flaring, 
deeply-lobed  mouth.  The  eggs,  when  ex- 
truded, are  enveloped  in  a  large  gelatinous 
capsule  (Fig.  216),  which  is  secreted  by  the 
large  flattened  nidamental  gland  (c)  on  the 
floor  of  the  body-cavity,  tied  down  at  each 
end  by  cord-like  membranes.  Usually  there 
are  two  nidamental  glands. 

The  earliest  phase  of  development  of  the  egg 
of  most  Cephalopods  (Sepia,  Loligo)  is  like  that  of  birds  and 
reptiles,  the  yolk  undergoing  partial  segmentation,  the  blasto- 
derm being  restricted  to  a  small  disk,  as  in  Vertebrates.  Even- 
tually the  blastoderm  encloses  the  whole  yolk,  the  mantle 
begins  to  form,  the  eyes  are  at  first  in-pushings  of  the  outer 
germ-layer,  and  the  mouth  appears.  The  digestive  tract 
originates  from  a  primitive  invagination  of  the  outer  germ- 
layer  (ectoderm),  as  in  Amphioxus,  Ascidians,  worms,  and 
some  Coelenterates.  About  the  tenth  day,  as  observed  by 
Ussow,  at  Naples,  the  gills,  siphon  or  funnel,  and  arms  arise, 


-After  Verrill. 


DEVELOPMENT  OF  CUTTLE-FISHES. 


279 


and  a  day  later  the  rudiments  of  the  ears,  of  the  pharynx 
and  salivary  glands  ;  while  a  day  or  two  after,  the  ventri- 
cle, auricles,  the  kidneys,  the  ink-sac,  and  liver  develop. 
Contrary  to  the  usual  rule  the  ganglia  arise  from  the  middle 
instead  of  the  outer  germ-layer.  After  this  the  germ  grad- 
ually develops  until  it  rises  above  the  surface  of  the  egg, 
and  soon  the  yolk  is  partly  absorbed  and  is  contained  in  a 


PIG.  217. 


PIG.  218. 


Fig.  217.— Embryo  of  Loligo  Pealii.    a,  a",  a'",  a"",  the  right  arms  belonging  to 
four  pairs  ;  c,  the  side  of  the  head  ;  «,  the  eye  ;  /,  the  caudal  fins ;  h,  the  heart ;  m, 


218  the  same.— Both  after  Verrill. 

large  yolk  sac,  as  in  Figs.  217,  218.  Finally  the  young  cut- 
tle-fish hatches  in  the  form  indicated  by  Fig.  219,  and  then 
swims  free  upon  the  surface  of  the  sea. 

The  development  of  Cephalopods  in  general  is,  then,  di-  (/ 
rect,  i.e.,  there  is  no  metamorphosis,  the  phases  of  meta- 
morphosis seen  in  most  other  mollusks  not  appearing  ;  but 
in  an  unknown  species  of  cuttle-fish  whose  eggs  were  found 
floating  on  the  Atlantic,  the  germ,  after  the  partial  segment- 
ation of  the  yolk,  assumed  a  trochosphere  condition  (Fig.  220) 
before  the  definitive  features  (Fig.  221)  of  the  cuttle-fish 


280 


ZOOLOGY. 


appeared.     The  squids  or  cuttle-fish  are  very  active,  some- 
times leaping  out  of  the  water  and  falling  on  the  decks  of 
large  vessels.     They  dart  rapidly  back- 
ward by  ejecting  the  water  from  their 
siphon  or  funnel. 

The  Cephalopods  are  divided  into 
two  orders,  according  to  the  number  of 
their  gills. 

Order  1.  Tetrabranchiata.  —  This 
group,  in  which  the  gills  are  four  in 
number,  is  represented  by  the  Nautilus, 
the  sole  living  representative  of  a  num- 
ber of  fossil  forms,  such  as  Orthoceras, 
Goniatites  and  Ammonites. 

Nautilus  pompilius  Linn.  (Pig.  222), 
and  Nautilus  umbilicatulus  are  the 
only  survivors  of  about  1500  extinct 
species  of  the  order. 

Order  2.  Dibranchiata.  —  The  Di- 
Iranchiates  are  so  called  from  possessing  but  two  gills,  while 
the  Tetrabranchiates  had,  as  in  Nautilus,  numerous  unarmed 
tentacles ;  these  are  now  represented  by  ten  (Decapoda).  or 


-of 


Fig.  219.— Same  as  Fig. 
218,  but  farther  advanced. 


FIG.  221. 

Fig.  220.— Development  of  an  unknown  cuttle-fish,  v,  velum  ;  y,  yolk ;  ml,  man- 
tle beginning  to  develop. 

Fig.  221.— The  same,  much  farther  advanced,  a,  a',  a",  arms  ;  m,  mouth  ;  br,  6r, 
gills  ;  /,  funnel ;  A,  ear  ;  g,  optic  ganglion  ;  mt,  mantle,  the  dotted  line  ending  in  a 
ifcromatophore. — After  Grenacher. 

eight  (Octopoda)  arms,  provided  with  numerous  suckers.    To 
the  ten-armed  forms  belong  Rpirula,  a  diminutive  cuttle,  with 


BELEMNITES. 


281 


an  internal  coiled  shell.     The  shells  of  Spirula  Peronii  La- 
marck are  rarely  thrown  ashore  on  Nantucket ;  it  lives  upon 


>i 

Pig.  222.— Pearly  Nautilus,  N.  pompilius.  Seen  in  section  showing 
the  chambers  and  siphuncle.  Half  natural  size.— From  Tenney's  Zo- 
ology. 

the  high  seas.     The  extinct  Belemnites  was  provided  with  an 
air-cavity  (phragmocone)  with  a  straight  shell,  the  "  thunder- 


Fig.  223.— Poulpe  or  Common  Octopus  of  Brazilian  Coast 

bolt"  fossil.    Allied  to  Loligo  and  Ommastrephes,  are  gigan- 
tic cuttle-fishes  which  live  in  mid-ocean,  but  whose  remains 


282 


ZOOLOGY. 


have  been  found  at  sea,  or  cast  ashore  at  Newfoundland  and 
the  Danish  coast ;  or  their  jaws  occur  in  the  stomach  of 
sperm  whales,  as  squid  of  all  sizes  form  a  large  proportion  of 
the  food  of  sperm  whales,  dolphins,  porpoises,  and  other 
Cetaceans  provided  with  teeth.  The  largest  cuttle-fish 
known  is  Architeutliis  princeps  Verrill,  the  body  of  which 
must  be  about  six  and  a  half  metres  (nineteen  feet)  in  length, 


and  nearly  two  metres 
(five  feet,  nine  inches) 
in  circumference.  The 
two  longer  arms  are  9 
metres  long.  Architeu- 
tliis monachus  Steen- 
strup  has  a  body  about 
two  metres  (seven  feet) 
long,  and  the  two  long- 
er arms  seven  metres 
( twenty  -  four  feet) 
long.  A  still  larger 
individual  was  esti- 
mated by  Verrill  to  be 
in  total  length  about 
fourteen  metres  (forty- 
four  feet).  It  is  some- 
times thrown  ashore 

on  the  coast  of  Newfoundland  and  Labrador,  and  in  one  in- 
stance attacked  two  men  in  a  boat. 

The  Octopus  (Fig.    223)   and  Aryonauta  represent  the 
eight-armed  forms. 


Pig.  224.— Octopus  Bairdil,  natural  size,  dorsal  and 
lateral  view.    Gulf  of  Maine.— After  Verrill. 


PAPER  NAUTILUS.  283 

Those  weird,  horrifying  creatures,  the  Octopi,  are  very  soft- 
bodied,  and  live  on  shore  just  below  or  at  low-water  mark,  or 
in  deeper  water.  They  have  no  shell  or  pen.  Octopus punc- 
tatus  Gabb  exp'ands  4£  metres  (14  feet)  from  tip  to  tip  of  the 
outstretched  arms.  They  are  brought  of  this  size  into  the 
markets  of  San  Francisco,  where  they  are  eaten  by  Italians 
and  Chinese.  An  Indian  woman  at  Victoria,  Vancouver 
Island,  in  1877,  was  seized  and  drowned  by  an  Octopus,  prob- 
ably of  this  species,  while  bathing  on  the  shore.  Smaller  spe- 
cies on  coral  reefs  sometimes  seize  collectors  or  natives,  and 
fastening  t)  them  with  their  relentless  suckered  arms  tire 
and  frighten  to  death  the  hapless  victim.  Octopus  Bairdii 
Verrill  (Fig.  224)  inhabits  the  Gulf  of  Maine  at  from  fifty 
to  one  hundred  fathoms. 

The  Argonauta,  or  paper  nautilus,  has  a  beautiful,  delicate 
shell.  A.  argo  lives  in  the  Mediterranean,  but  in  rare  cases 
has  been  thrown  ashore  at  New  Jersey  and  Florida.  The 
animal  lives  in  the  shell,  but  is  not  permanently  attached  to 
it,  the  shell  not  being  chambered,  and  holds  on  to  the 
sides  by  the  greatly  expanded  terminations  of  two  of  its 
arms,  which  secrete  the  shell.  The  males  are  very  small,  not 
more  than  five  centimetres  (one  inch)  in  length.  During 
the  reproductive  season  the  third  left  arm  becomes  larger 
and  different  in  form  from  the  others,  and  becoming  encysted 
is  finally  detached  from  the  body,  and  deposited  by  the  male 
within  the  mantle-cavity  of  the  female,  where  the  eggs  in  a 
way  unknown  are  fertilized  by  the  spermatic  bodies.  The 
free  arm  was  supposed  originally  to  be  a  parasitic  worm,  and 
was  described  under  the  name  of  Hectocotylus. 

The  living  species  of  Cephalopods  have  a  wide  geographi- 
cal range,  and  a  high  antiquity,  the  earliest  forms  appearing 
in  the  Lower  Silurian  Period,  while  the  type  culminated  in 
the  Liassic,  Jurassic  and  Cretaceous  Periods. 


CLASS  III.— CEPHALOPODA. 

Mollusks  with  the  head-lobe  divided  into  arms,  usually  provided  with 
suckers  ;  eyes  more  highly  organized  than  in  any  other  invertebrates  ; 


284  ZOOLOGY. 

nerwus  ganglia  much  concentrated  and  protected  by  an  imperfect  cartila- 
ginous capsule  ;  pharynx  armed  with  two  teeth  like  a  parrot's  beak,  be- 
sides an  odontophore.  Sexes  distinct.  Usually  development  is  direct, 
with  no  metamorphosis  ;  segmentation  of  the  yolk  partial,  and  a  primi^ 
tive  streak  is  present  as  in  birds  and  reptiles. 

Order  1.  Tetrabranchiata.— With  four  gills.  (Nautilus,  living  ;  Or- 
thoceras,  Goniatites,  Ammonites,  extinct.) 

Order  2.  Dibranchiata.—  With  two  gills.  (Spirula,  Belemnites,  ex- 
tinct, Sepia,  Architeuthis,  Loligo,  Ommastrephes,  Octopus 
Argonauta.) 

TABULAR  VIEW  OP  THE  CLASSES  OP  MOLLUSCA. 

Cephalopoda. 


Cephalophora. 

Lamellibranchiata. 


MOLLUSCA. 

Laboratory  Work. — The  cuttles  are  not  easy  to  dissect.  A  horizon- 
tal section  through  the  head  will  show  the  relations  of  the  cartilaginous 
capsule  to  the  brain,  optic  nerves  and  eyes.  The  nervous  ganglia  can 
only  be  traced  after  tedious  dissection.  To  study  the  viscera  freshly- 
killed  specimens  are  quite  essential. 


GENERAL  CHARACTERS  OF  ARTHROPODS.       285 


CHAPTER  VII. 

BRANCH  VII.— AETHROPODA  (CRUSTACEANS  AND 
INSECTS). 

General  Characters  of  Arthropods. — To  this  group  be- 
long those  Articulates  which  have  jointed  appendages,  i.  e., 
antennae,  jaws,  maxillae  (or  accessory  jaws),  palpi,  and  legs 
arranged  in  pairs,  the  two  halves  of  the  body  thus  being 
more  markedly  symmetrical  than  in  the  lower  animals.  The 
skin  is  usually  hardened  by  the  deposition  of  salts,  carbon- 
ate and  phosphate  of  lime,  and  of  a  peculiar  organic  sub- 
stance, called  chitine.  The  segments  (somites  or  arthro- 
meres)  composing  the  body  are  usually  limited  in  num- 
ber— twenty  in  the  Crustaceans  and  eighteen  in  the  insects — 
while  each  arthromere  is  primarily  divided  into  an  upper 
(tergum),  lower  (sternum),  and  lateral  portion  (pleurum). 
These  divisions,  however,  cannot  be  traced  in  the  head  either 
of  Crustaceans'or  insects.  Moreover  the  head  is  well  marked, 
with  one  or  two  pairs  of  feelers  or  antennae,  and  from 
two  to  four  pairs  of  biting  mouth-parts  or  jaws,  and  two 
compound  eyes  ;  besides  the  compound  eyes  there  are  simple 
eyes  in  the  insects.  The  germ  is  three-layered,  and  there  is 
usually  a  well-marked  metamorphosis.  The  Arthropoda 
are  nearest  related  to  the  worms,  certain  Annelides,  with 
their  soft- jointed  appendages  (tentacles  as  well  as  lateral 
cirri)  and  well-marked  head  anticipating  or  foreshadowing 
the  Arthropods.  On  the  other  hand,  certain  low  parasitic 
Arthropods,  as  Linguatula,  have  been  mistaken  for  genuine 
parasitic  worms.  So  close  are  the  affinities  of  the  Vermes 
and  Arthropods  that  they  were  by  Cuvier  united  as  a  Branch 
Articulata,  and  while  the  Annelides  and  Arthropods  may 
have  had  a  common  parentage,  the  recent  progress  in  our 
knowledge  of  the  worms,  has  led  naturalists  to  discard  the 


286  ZOOLOGY. 

Articulata  of  Cuvier  as  a  heterogeneous  assemblage  of 
forms  embracing  at  least  three  branches  of  the  animal  king- 
dom, namely,  the  Vermes, 
Tunicata,  and  Arthropo- 
da. 

The  Arthropoda  are  di- 
vided into  two  well-de- 
fined classes,  i.  e.,  the 
Crustacea  with  two  body- 
regions,  the  head-thorax 

Fig.    225.-Shrimp,  Palcemonetes  vulgaris.     and    abdomen    (Fig.  225), 
«,  cephalo-tliorax :  0,  abdomen.  .,      .          .,  .  V 

and    breathing     through 

the  body-walls  or  by  external  gills ;  and  the  Insecta  ( Tra- 
cheata),  in  which  the  arthromeres  are  grouped  into  three 
body-regions,  i.  e.,  a  head,  thorax,  and  abdomen  ;  and  which 
breathe  by  internal  air-tubes  (tracheae). 


CLASS  I. — CRUSTACEA  (Water-fleas,  Shrimps,  Lobsters, 
and  Crabs). 

General  Characters  of  Crustaceans. — The  typical  forms 
of  this  class  are  the  craw-fish,  lobster,  and  crab,  which  the 
student  should  carefully  examine  as  standards  of  comparison, 
from  which  a  general  knowledge  of  the  class,  which  varies 
greatly  in  form  in  the  different  orders,  may  be  obtained. 
The  following  account  of  the  lobster  will  serve  quite  as  well 
for  the  craw-fish,  which  abounds  in  the  rivers  and  streams 
of  the  Middle  and  Western  States. 

The  body  of  the  lobster  consists  of  segments  (somites, 
arthromeres),  which  in  the  abdomen  are  seen  to  form  a  com- 
plete ring,  bearing  a  pair  of  jointed  appendages,  which  are 
inserted  between  the  sternum  and  tergum,  the  pleurum  not 
being  well  marked  in  the  abdominal  segments.  The  abdo- 
men consists  of  seven  segments.  One  of  these  segments 
(Fig  226  D')  should  be  separated  from  the  others  by  the  stu- 
dent, in  order  to  observe  the  mode  of  insertion  of  the  legs. 
Each  segment  bears  but  a  single  pair  of  appendages,  and  it 


EMBRYOLOGY  OF  BARNACLES. 


295 


was  at  first  thought  to  be  an  adult  Crustacean,  and  described 
under  the  name  of  Nauplius.  The  Nauplius 
of  the  genuine  barnacles  (Fig.  232)  has  three 
pairs  of  legs  ending  in  long  bristles,  with  a 
single  eye,  and  a  pair  of  antennae,  the  body 
ending  in  front  in  two  horns,  and  posteriorly 
in  a  long  caudal  spine.  After  swimming 
about  for  a  while,  the  Nauplius  attaches  it- 
self to  some  object  by  its  antennae,  and  now  a 
strange  transformation  results.  The  body  is 
enclosed  by  two  sets  of  valves,  appearing  as  if  Mie*  Darwin, 
bivalved,  like  a  Cypris  (Fig.  233) ;  the  peduncle  grows  out, 


Pig.  231. —Comple- 
mentary male  of  Seal- 
pettum  regium,  greatly 
enlarged. —After  Wy- 
v  ilia-Thompson. 


Fig.  %to.—Scalpellum  regium.  a,  complementary 
male,  lodged  within  the  valves.  —  After  Wyville- 
Thompson. 


296 


ZOOLOGY. 


concealing  the  rudimentary  antennae,  and  the   feet 
smaller,  and  eventually  the  barnacle-shape  is  attained. 


grow 
The 


Fig.  233.— Pupa  of  Lepast  much  en- 
larged.— After  Darwin. 


Pig.  233.— Nauplius  of  Bcdanus  bcit- 
noicles, 


much  enlarged. 


common  barnacle  (Balanus  balanoides)  attains  its  full  size, 
after  becoming  fixed,  in  one  season,  i.  e.9  between  the  first  of 
April  and  November. 

Still  lower  than  the  genu- 
ine barnacles  are  the  root-bar- 
nacles or  Rhizocephala,  repre- 
sented by  Peltogaster  (Fig. 
234)  and  Sacculina  (Fig.  235), 
in  which  the  young  is  a  more 
simple  Nauplius  form,  like 
the  young  of  the  Entomostra- 
ca,  while  the  adult  is  a  sim- 
ple sac,  containing  no  diges- 
tive organs  or  nerves.  From 
the  feet  of  the  young  grow 
out,  after  the  animal  becomes 
sessile,  long  root -like  fila- 
ments, which  ramify  in  the 
body  of  the  crab,  to  which 
these  animals  are  firmly  an- 
chored. We  can  conceive  of 

no  lower,  more  degraded  Crus-    times.-From  BreWs  Thierleben. 

tacean  than  these  root-barna- 
cles, the  only  signs  of  life  being  the  powerful  contractions 
of  the  roots  and  an  alternate  expansion  and  contraction  of 


Fig.  234.  —  Peltogaster  curvatiis,  en- 
larged li  times,  beneath  the  larva  or  Nau- 
plius of  Parthenopea,  enlarged  about  200 


ENTOMOSTRACA. 


297 


the  body,  forcing  the  water  into  the  brood-cavity,  and  again 
expelling  it  through  a  wide  orifice.  These  root-barnacles 
recall  the  Trematode  worms,  though  the 
/^PIIldBfelfcK  latter  are  much  more  highly  organized. 
(I  JP  An  allied,  form  (Cryptophialus  minutus) 

,J/ifjjj£r     undergoes  the  larval  or  Nauplius  stage 
in  the  egg,  hatching  in  the  pupa  condi- 
Fig.  M5*saccuiinacar.  tion,  while  another  form  (a  species  of 
Peltogaster  9)  also  leaves  the  egg  in  the 


Order  2.  Entomostraca  (Water-fleas). 
— The  type  of  this  group  is  Cyclops  (Fig.  236,  C.  quad- 
ricornis,  see  also  Fig.  237)  in  which  the  body  is  pear- 
shaped,  with  a  single  bright  eye  in 
the  middle  of  the  head ;  two  pairs 
of  antennae,  used  for  swimming  as 
well  as  sense-organs ;  biting  mouth- 
parts,  and  with  short  legs.  The 
sexes  are  distinct,  the  females  swim- 
ming about  with  two  egg-masses 
attached  to  the  base  of  the  ab- 
domen. The  young  is  a  Nauplius, 
much  like  that  represented  in  Fig. 
234,  the  mouth-organs,  the  legs 
and  abdominal  segments  arising 
after  successive  moults,  until  the 
adult  form  is  attained.  Allied  to 
Cyclops  is  Canthocamptus  caver- 
narum  Packard  (Fig.  238),  an  eyed 
species,  living  in  Willie's  Spring,  in 
Mammoth  Cave. 

Many  Entomostraca  are  parasitic, 
and  consequently  undergo  a  retro- 
grade development,  losing  the 
jointed  structure  of  the  body,  the 
appendages  being  more  or  less 
aborted,  while  the  body  increases 
greatly  in  size.  Such  are  the  fish-lice,  represented  by  the 
Lerncea  of  the  cod. 


eye ; 
/>  feet.— After 


298 


ZOOLOGY. 


oe 


Fig.  237.— Intestine  and  testis  (t)  of  a  copepod 
(Pleuroma),  side  view.  «,  oesophagus  ;  t>,  stomach ; 
h,  blind  sac  leading  from  the  stomach  ;  i,  intes- 
tine; c,  heart ;  vd,  coiled  vas  deferens.—  After  Claus, 
from  Gegenbaur. 


In  Lerneonema  radiata  Steenstrup  and  Lutken  (Fig.  239), 
we  find  the  lowest  term  in  the  series  of  degradational  forms 

of  this  order.  The 
mouth-parts  are  here 
converted  into  five 
roots,  radiating  from 
the  head  ;  the  body 
is  not  segmented,  and 
ends  in  two  long  egg- 
masses. 

In  Penella  (Fig. 
241)  the  body  is  cord- 
like,  buried  in  the 
flesh  of  the  sun-fish  or  sword-fish,  etc.,  the  females  having 
two  long,  string-like 
egg-sacs.  The  speci- 
men figured  was  taken 
from  a  sword-fish  off 
Portland,  Maine. 

In  Lerncea  branchia- 
lis  Linn,  of  the  gills  of 
the  cod,  the  body  is 
thicker,  the  root-like 
appendages  grow  deep 
into  the  flesh  of  its 
host,  like  twisted  and 
gnarled  roots,  while  the 
shapeless  sac-like  body 
is  filled  with  eggs. 

In  Adheres,  we  as- 
cend a  step  higher  in 
the  perfection  of  or- 
gans ;  the  creature  is 
attached  by  a  pair  of 

vT-4-^     4-         Fig>  238-—  Oanthocamptus  caver-       Fig.  239.- 
jaWS     WnlCn     Unite     10   narum  of  Mammoth  Cave,  much    Fish -louse  of 

form  a  sucker,  the  an-  enlarged-  MRSSt 

tennaa  are  present,  though  rudimentary,  while  -AfterVernlL 
the  abdomen  is  faintly  segmented.  A.  Carpenteri  Packard 
(Fig.  240)  lives  on  the  trout  in  Colorado, 


CLADOCERA. 


299 


Fig.  240.— Actheres  of  the  trout 


The  highest  members  of  the  group  of  sucking  Entomo- 
straca  are  Caligus  and  A  rgulus,  in  which  the  body  ij  seg- 
mented, with  antennae  and  free 
mouth-parts  and  legs ;  the  latter 
genus  with  compound  eyes.  Cali- 
gus curtus  Mtiller  lives  on  the  cod, 
and  Argulus  aloscB  Gould  on  the 
alewife. 

Order  3.  Branchiopoda.  —  This 
order  includes  such  Crustacea  as 
in  the  higher  forms  breathe  by 
rather  broad  feet  There  is  a  con- 
siderable range  of 
form  from  the 
Ostracoda,  repre- 
sented by  Cypris, 
in  which  the  feet 
are  much  as  in  Cy- 
clops, through  Daphnia  and  Sida  (Fig.  242) 
which  represent  the  Cladocera,  up  to  the 
Phyllopods.  The  suborder  of  Ostracoda 
( Cypris)  are  bivalved,  the  shell  often  thick. 
They  have  two  eyes,  two  pairs  of  antennae, 
a  pair  of  mandibles  with  a  jointed  feeler 
(palpus)  and  a  gill,  and  four  pairs  of  feet, 
the  second  pair  often  carrying  a  small  gill. 
The  shells  of  certain  species  allied  to  Cypris 
abound  in  the  lowest  Silurian  strata.  The 
species  live  in  fresh-water  pools  and  in  the 
ocean  at  various  depths.  They  undergo  no 
metamorphosis,  the  youngest  stage  being  a 
shelled  Nauplius. 

The  suborder  Cladocera  is  represented  by^ 
fresh  and  salt-water  species.  The  higher 
forms  are  Sida  and  Daphnia.  They  are 
called  water-fleas  from  their  jerky  motions. 
The  eggs  of  Daphnia  are  borne  about  by 
Pig  24i  — Peneiia  of  the  females  in  so-called  brood-cavities  on 

the  sword-fish,  female.  ^  back  under   ^   ghelL       There   are   two 

sorts  of  eggs,  i.  e.,  the  "summer"  eggs,  which  are  laid  by 


300  ZOOLOGY. 

asexual  females,  the  males  not  appearing  until  the  autumn, 
when  the  females  lay  the  fertilized  "winter"  eggs,  which  are 
surrounded  by  a  very  tough  shell.  Dohrn  observed  the  de- 
velopment of  the  embryo  in  the  summer  eggs.  At  first  the 
embryo  has  but  three  pairs  of  appendages,  representing- the 
antennae  and  one  pair  of  jaws.  It  is  thus  comparable  with 
the  Nauplius  of  the  Copepodous  Entomostraca,  and  thus  the 


Fig.  242.— Sida.    «,  egg  in  brood-sac. 

Cladocera  may  be  said  to  pass  through  a  Nauplius  stage  in 
the  egg. 

Afterwards  more  limbs  grow  out,  until  finally  the  embryo 
is  provided  with  the  full  number  of  adult  limbs,  and  hatches 
in  the  form  of  the  mature  animal,  undergoing  no  farther 
change  of  form. 

The  members  of  the  suborder  Phyllopoda  are  more  highly 
developed  than  any  of  the  Crustacea  mentioned,  though,  like 
the  Ostracodes  and  Cladocera,  the  body  is  usually  partly 
covered  by  a  large  carapace  (the  mandibular  segment  greatly 
developed),  which  is  sometimes  bent  down,  and  opens  and 
shuts  by  an  adductor  muscle,  so  that  they  resemble  bivalve 


P1TTLLOPODA. 


301 


Mollusca  But  they  are  especially  characterized  hy  the 
broad  leaf -like  feet,  subdivided  into  lobes,  and  adapted  for 
breathing  as  well  as 
for  swimming.  The 
thorax  merges  insens- 
ibly into  the  abdomen. 
The  number  of  body- 
segments  varies  great- 
ly, there  being  six- 
teen in  LimnetiSy  the 
simplest  form,  and 
sixty -nine  in  Apus, 
or  three  times  the 
number  present  in  the 

lobster,  the  Segments      Fig.  Z&.—Limnetis  GvuldU,  much  enlarged.— After 

thus  being  irrelatively  Burge88< 

repeated,  a  sign  of  inferiority.     There  is  a  pair  of  simple 
eyes  consolidated  into  one  as  in  Limnetis  and  Limnadia,  or 

as  in  Apus,  there  is  a 
pair  of  compound  eyes, 
situated  in  the  cara- 
pace, apparently  on 
one  of  the  antennal 
segments.  In  Bra;i- 
chipus  and  Artemla 
the  compound  eyes 
are  stalked,  an  antic- 
ipation of  the  stalked 
eye  of  the  lobster, 
etc.,  but  the  eye,  it 
should  be  noticed,  is  not  developed  from  a  separate 
segment,  but  from  one  of  the  two  antennal  segments.  All 
the  members  of  this  order  hatch  in  the  Nauplius  form,  the 
three  pairs  of  appendages  of  the  larva,  representing  the  two 
pairs  of  antennae  and  the  mandibles  of  the  adult.  The  spe- 
cies live  in  pools  of  fresh  water  liable  to  dry  up  in  summer  ; 
they  lay  eggs  which  drop  to  the  bottom,  and  show  great  vi- 
tality, withstanding  the  heat  and  dryness  after  the  water 
has  evaporated  ;  the  young  hatching  after  the  rains  refill  the 
pools  or  ditches. 


Pig.  244.— Limnadia  Agassizii,  enlarged. 


302 


ZOOLOGY. 


This  suborder  presents  a  beautiful  series  of  increasingly 
complex  forms,  as  we  ascend  from  Limnetis  to  Branchipus. 
In  Limnetis  the  bivalve  shell  encloses  the  ani- 
mal,  and  is  the  size  of  a  small  flattened  pea. 
|  There  are  from  ten  to  twelve  feet -bearing 
V  segments.  L.  Gouldii  Baird  (Fig.  243)  is  very 
]f  rare  in  Canada  and  New  England.  The  shell 
of  Limnadia  is  thin,  oval,  and  there  are  from 
eighteen  to  twenty-six  feet-bearing  segments. 
L.  (Eulimnadia)  Agassizii  Packard  (Figs.  244 
and  245)  inhabits  pools  in  Southern  New  En- 
gland. The  shell  of  Esfheria  (Fig.  246,  Es- 
Meria  Belfragei  Packard)  is  sometimes  mis- 
taken  for  that  of  the  fresh -water  mollusks 
Oyclas  and  Pisidium.  The  males  of  the  fore- 
going genera  have  the  first  pair  of  feet  modi- 
fied to  form  large  claspers  (Fig.  245). 

In  Apus  the  abdomen  projects  beyond  the  large  carapace, 
and  ends  in  two  long  many-jointed  appendages.  There  are 
about  sixty  pairs  of  feet,  each  foot 
divided  into  several  leaf -like  lobes, 
wherein  respiration  is  carried  on. 

These  Phyllopods  usually  swim  upon 
their  backs,  as  in  the  species  of  Bran- 
chipus.  The  females  chiefly  differ 
from  the  males  in  the  presence  of  an 
orbicular  egg-sac  on  the  eleventh  pair 
of  feet,  the  sac  being  a  modification  of 
two  of  the  lobes  of  the  feet,  and  containing  but  a  few  eggs. 
Apus  CBqualis  Packard  (Fig.  247,  Fig.  249  A,  represents  the 
larva  of  a  European  Apus)  inhabits  pools  in  the  western 
plains.  Lepidurus  differs  from  Apus  in  having  the  telson 
spoon-shaped  instead  of  square.  L.  Couesii  Packard  (Fig. 
248)  occurs  on  the  Rocky  Mountain  plateau  in  Utah  and 
Montana.  It  is  an  interesting  fact  in  zoo-geography  that 
there  are  no  species  of  Apus  and  Lepidurus  east  of  the  west- 
ern plains.  Apus  has  been  found  by  Siebold  to  reproduce 
parthenogenetically. 

The  various  species  of  Branchipus  end  Artemia  have  no 


times. 


246.— Shell  ofEstheria 
enlarged  three 


PHYLLOPOD   CRUSTACEANS. 


303 


carapace,  the  mandibular  segment  being  small  and  not  over- 
lapping the  segments  behind  it.     The  second  antennas  are 


Fig.  248.—Lepidurus  Couesii, 
side  and  dorsal  view,  natural 
size. 


Fig.  247. — Apus  aqualis,  natural  size. 

large  and  in  the  male  adapted  for 
clasping.  In  Thamnocephalus  (Fig. 
250,  T.  brachyurus  Packard,  from 
Kansas)  there  is  a  singular  shrub- 
like  projection  of  the  front  of  the 
head,  and  the  abdomen  is  spatulate 
or  spoon-shaped  at  the  end.  Bran- 
cMnectes  Color adensis  Pack.  (Fig. 
251)  is  a  Eocky  Mountain  form.  ?fe-  249.-^,  Larva  of  Apus  can- 

7  J  cnformts.  —  After   Zaddach.      6, 

Ihe    brine  -  Shrimp,   Artemia,  lives   Naupliusof  Artemia  salina  ofEn- 

only   in   brine-vats   or  in  the  salt 

lakes  of  the  West  and  of  Southern  Europe.     Artemia  gra- 

cilis  Verrill  (Fig.  252)  has  thus  far  only  been  found  in  tubs 


304 


ZOOLOGY. 


of  concentrated  salt  water  on  railroad  bridges  in  New  En- 
gland.    Artemia  fertilis  Verrill  abounds  in  Great  Salt  Lake. 


Kg.  2Sto.—Thamnocephalus  platyurus,  male,  natural  size,  side  and 
head  of  the  female  ;  6,  end  of  the  body  of  the  female,  showing  the 


and  front  view,    a, 
ovisac. 


They  may  often  be  seen  swimming  about  in  pairs,  as  in 
Fig.  253.     This  species  has  a  Nauplius  young  like  that  of 


Fig.  y&l.—Branchinectes  Coloradensis  Pack. 

the  brine-shrimp  of  Europe  (Fig.  249  b).  It  is  a  signifi- 
cant fact,  bearing  on  the  question  of  the  origin  of  species, 
that,  according  to  Schmankiewitsch,  Artemia  may  change  its 


TETRA  DEC  A  PODS. 


305 


form,  the  change  being  induced  by  the  greater  or  less  saltness 
of  the  water.  Artemia  produces  young  by  budding  (parthe- 
nogenesis) as  well  as  from  eggs. 
A  species  observed  near  Odessa 
produced  females  alone  in  warm 
weather;  and  only  in  water  of  rf 
medium  strength  were  males 
produced.  The  eggs  of  Arte- 
mia fertilis  have  been  sent  in 
moist  mud  from  Utah  to  Mu- 
nich, Germany,  and  specimens 
raised  from  the  eggs  by  Siebold, 
proving  the  great  vitality  of  the 
eggs  of  these  Phyllopods,  a  fact 
paralleled  by  the  similar  vitality 
of  the  eggs  of  the  king-crab. 
Fig.  249  b  represents  the  Nau- 
plius  of  the  European  brine- 
shrimp. 

Order  4.  —  Tetradecapoda. — 
To  this  order  belong  the  sow- 
bugs  (Isopoda)  and  the  beach- 
fleas  (Amphipoda).  In  these 
Crustacea  there  is  no  cephalo- 
thorax,  but  the  head  is  small,  — After  Verrffl.' 
bearing  two  pairs  of  antennae,  and  a  pair  of  jaws,  and  three 
pairs  of  maxillae.  The  thorax  is  continuous  with  the  abdo- 
men. Eespiration  is  performed  by  lamellate  or  leaf -like 
gills  on  the  middle  feet  in  the  Amphipods,  or  on  the  hinder 

abdominal  feet  in 
the  Isopods.  The 
lowest  Isopods  are 
parasitic,  they 
graduate  into  the 
Amphipods,  and 
the  higher  Amphipods  are  connected  with  the  shrimps  (De- 
capoda)  through  a  group  (probably  a  suborder)  of  synthetic 
forms  (Palceocaris,  Acanthotelson  and  Gampsonyx,  Fig. 
254)  such  as  are  found  in  the  coal  formation  of  Illinois 


Fig.    252.— Brine  -  shrimp,    Artemia 
gracilis,  enlarged,    a,  first  antenna  ;  b. 


Fig.  253.— Artemia  fertilis   from 
egg-sac  ;  c,  male  claspers. 


Great   Salt   Lake,    e, 


806 


ZOOLOGY. 


and    Europe,  which    may    be    called    Antliracarida,   and 
which  have  antennae  and  tails  like  shrimps,  but  the  body 


Fig.  254.—  Gampsonyx  fimto'iatits  of  European  coal 
eize. 


m 

times  natural 


and  limbs  like  Amphipods.     In  the  Isopods  the  body  is  flat- 
tened and  the  head  rather  broad. 

Fig.  256  is  a  dorsal  view  of  Serolis  Gau- 
dicTiaudi  Audouin  and  Edwards,  with  the 
two  pairs  of  antennae  and  pointed  sides  of 
each  thoracic  segment,  dissected  to  show  the 
nervous  system,  the  two  pairs  of  antenna! 
nerves ;  the  optic  nerves  (op)  sent  to  the 
compound  eyes.  Fig.  257  represents  a  trans- 
verse section  of  the  body,  showing  the  mode 
of  insertion  of  the  legs,  and  the  equality  in 
the  tergal  and  sternal  sides  of  the  body. 
Fig.  259  represents  a  gill.  In  the  common 
pill-bug  (Porcettio)  aerial  respiration  is  per- 
formed by  respiratory  cavities  situated  in 
the  abdomen.  In  Tylos  similar  cavities  are 
filled  with  a  multitude  of  branching  co3ca, 
serving  for  aerial  respiration,  thus  antici- 
pating the  tracheary  system  of  insects. 
The  nervous  system  is  quite  simple.  (Fig. 
255,  Idotwa,  and  Fig.  256,  that  of  Serolis.) 
The  digestive  canal  is  straight,  consisting 
.  255.— Nervous  of  a  short  oesophagus,  a  membranous  stoin- 
— DrawnBby*jT  ach,  and  usually  a  short  tubular  intestine  ; 
the  liver  consisting  of  several  short  coeca. 
In  Serolis  Gaudichaudi  the  stomach  is  somewhat  pear- 


EMBRYOLOGY  OF  ONISCU8.  307 

shaped,  widest  behind,  extending  a  little  behind  the  middle 
of  the  body.  The  intestine  is  about  one  half  as  wide  as  the 
stomach. 


Fig.  256.—  Dissection  of  Scrolls  to  show  the  nervous  system.— Dissected  and  drawn 
by  J7S.  Kingsley. 

There  is  no  coecal  enlargement,  and  no  "urinary"  tubes. 
The  sexes  are  distinct.  The  young  are  hatched  in  the  form 
of  the  adult,  there  being  no  metamorphosis. 

The  development  of  the  pill-bug,  Oniscus  murarius,  is 
probably  typical  of  that  of  most  Tetradecapods  and  Deca- 


Fig.  257.— Transverse  section  of  Serolis.  t,  I,  tergum  ;  s,  s,  sternum  ;  em,  epime- 
rum  ;  es,  episternum,  at  insertion  of  the  legs.— Prepared  and  drawn  by  J.  S.  Kings- 
ley. 

pods  (Bobretzky).     The  first  change  after  fertilization  is  the 
origin  of  the  formative  or  primitive  blastodermic  cells  at  one 


308 


ZOOLOGY. 


pole  of  the  egg.  This  single  cell  subdivides,  its  products 
forming  the  "  blastodermic  disk"  or  outer  germ-layer,  the 
segmentation  of  the  yolk  being  partial.  The 
third  (innermost)  and  middle  germ-layers  next 
arise  (the  same  processes  go  on  in  certain 
shrimps,  viz.  :  Crangon  and  Palcemori).  The 
intestine  is  formed  by  an  in -pushing  of  the 
outer  germ-layer.  The  limbs  now  bud  out,  the 
result  of  the  pushing  out  of  the  outer  germ- 
layer  (ectoderm).  The  nervous  cord  arises  from 
the  ectoderm ;  the  large  intestine  originates  in 
the  yolk-sac,  its  epithelium  first 
appearing  in  the  liver-sac.  The 
heart  is  the  last  to  be  formed.  Ex- 
ternally the  antennae  in  Oniscus 
and  also  Asellus  are  the  first  to  bud 
out ;  the  remaining  appendages  of 
the  head  and  thorax  arise  contem- 


Fig.    258.— 
tn-parts  of 


Mout 

Serolis'm,  man- 
dible ;  mx',  first 
maxilla  ;  mx", 

second  maxilla ;    poraneously,  and  subsequently  the 

mp,     m&xillary     x  J '  J 

palpus.— Drawn 
by  J.  S-  Kings- 
ley. 


Fig.  259.— A 
gill  of  Serolis.— 
Drawn  by  J.  S. 
Kingsley. 


abdominal  feet.     The  abdomen  in 
the  Isopods  is  curved  upwards  and 
backwards,  while  in  the  embryo  Amphipods  it  is  bent  be- 
neath the  body. 

The  development  of  the  Amphipods  or  beach-fleas  is 
nearly  identical  with  that  of  the  Isopods.  The  eggs  of  cer- 
tain species  undergo  total  segmentation,  while  those  of  other 
species  of  the  same  genus  (Grammarus)  partially  segment,  as 
in  the  spiders,  and  in  a  less  degree  the  insects. 

Standing  next  below  Cymothoa,  which  is  of  the  general 
Isopod  shape,  but  which  lives  parasitically  on  the  tongue 
and  other  parts  of  fishes,  but  which  from  their  parasitic 
habits  become  slightly  changed  in  form,  the  females  espe- 
cially, sometimes  becoming  blind,  is  the  family  of  which 
Bopyrus  is  a  representative.  The  females  (Fig.  262)  are  par- 
asitic under  the  carapace  of  various  shrimps.  In  B.  pandal- 
icola  Packard  n.  sp.,  the  females  are  many  times  larger  than 
the  males ;  the  ventral  side  of  the  body  is  partly  aborted, 
having  been  absorbed  by  its  pressure  against  the  carapace 
of  its  host,  which  is  swollen  over  it  ;  it  retains  its  position  by 


1SOPODA. 


309 


FIG.  262. 

Fig.  260.— Section  of  the  embryo  pilUbug.  </,  intestine;  L  epithelium  form- 
ing the  walls  of  the  two  lobes  of  the  liver  ;  g,  transverse  section  of  the  nervous  cord  ; 
A,  walls  of  the  body.— After  Bobretzky. 

Fisr.  261.— Section  of  more  advanced  embryo  pill-bug,  h,  heart ;  hi),  hypoder- 
mal  layer  or  body-walls  ;  m,  muscular  wall  of  the  intestine ;  e,  epithelial  lining  of  the 
intestine ;  ;>,  dividing  cell-wall  between  the  heart  and  intestine ;  /,  two  lobes  of  the 
liver  ;  g,  ganglion,  the  clear  space  being  filled  with  the  tine  granular  substance  of  the 
ganglion.— After  Bobretzky. 

Fig.  Zf&.—Bopyrus.  A,  ventral,  B,  dorsal  side  of  the  female ;  C,  lateral  and  Z>, 
dorsal  view  ot  the  male  ;  c1,  head  and  first  thoracic  segment ;  c2,  antennae— all  en- 
larged.—Packard,  del. 


310  ZOOLOGY. 

the  sharp  hook-like  legs  around  the  margin  of  the  body.  The 
head  has  no  eyes  nor  appendages.  The  male  (Fig.  262,  C,  D) 
is  but  slightly  modified,  is  very  minute,  and  is  lodged  partly 
out  of  sight  under  the  ventral  plates  of  the  female,  whose 
body  is  about  five  millimetres  (a  fifth  of  an  inch)  in  length. 


Fig.  263.—  Arcturus  2to$frii,with  its  young  clinging  to  its  antennae.—  After  Wyville- 
Thompson. 

Various  species  of  Porcellw  (sow-bugs)  live  under  stones 
on  land ;  and  allied  to  Asellus,  the  water  sow-bug,  is  the 
marine  Limnoria  lignorum  White,  which  is  very  injurious 
to  the  piles  of  bridges,  wharves,  and  any  submerged  wood. 
The  highest  Isopods  are  Idotcea,  of  which  /.  irroratus  Say 
(Fig.  255)  is  our  most  abundant  species,  being  common  in 
eel-grass,  etc.,  between  and  just  below  tide-marks  ;  and^rc- 
turus  (Fig.  263,  A.  Baffini  Sabine),  from  the  Arctic  seas. 


PHYLLOGARIDA.  311 

The  series  of  Amphipods  begins  with  Cyamus  ceti  (Linn.), 
the  whale-louse,  passes  into  Caprella,  with  its  linear  body 
and  spider-like  legs,  to  Hyper ia,  which  lives  as  a  mess-mate 
of  the  jelly-fish,  Cyanea,  and  culminates  in  the  water-flea 
(Gammarus  ornatus  Edwards)  and  sand-flea  ( Orchestia  agilis 
Smith),  abundant  and  leaping  in  all  directions  from  under 
dried  sea-weed  at  high-water  mark. 

Fig.  264  represents  Gammarus  robustus  Smith,  a  fresh- 
water form  common  in  the  western  territories. 


Fig.  264.—  Gammarus  robustus  Smith.    Utah.    Enlarged.— After  Smith. 

Order  5.  Pliyllocamda. — This  name  is  proposed  for  a 
group  of  Crustacea,  the  forerunner  of  the  Decapoda  and 
hitherto  regarded  as  simply  a  family  (NebaUada),  in  which 
there  is  an  interesting  combination  of  Copepod,  Phyllopod, 
and  Decapod  characters,  with  others  quite  peculiar  to  them- 
selves. The  type  is  an  instance  of  a  generalized  one,  and  is 
very  ancient,  having  been  ushered  in  during  the  earliest  Si- 
lurian period,  when  there  were  (for  Crustacea)  gigantic  forms 
(Ditliyrocaris  was  over  one  foot  in  length)  compared  with 
those  living  at  the  present  day.  The  order  connects  the 
Decapods  with  the  Phyllopods  and  lower  orders.  The  mod- 
ern Nebalia  is  small,  about  a  centimetre  (.40-.  50  inch)  in 
length,  with  the  body  compressed,  four  of  the  abdominal 
segments  projecting  beyond  the  carapace,  the  last  abdominal 
segment  bearing  two  large  spines.  There  is  a  large  rostrum 
overhanging  the  head  ;  stalked  eyes,  and  two  pairs  of  anten- 
nae, the  second  pair  nearly  as  long  as  the  body  and  many- 
jointed.  The  mandibles  are  succeeded  by  two  pairs  of  max- 


312  ZOOLOGY. 

illae.  Behind  these  mouth-parts  are  eight  pairs  of  short,  leaf- 
like  respiratory  feet,  which  do  not  project  beyond  the  edge  of 
the  carapace.  These  are  succeeded  by  four  pairs  of  large, 
long  swimming  feet,  and  there  are  two  additional  pairs  of 
small  abdominal  feet.  There  is  no  metamorphosis,  develop- 
ment being  direct,  the  young  hatching  in  the  form  of  the 
adult.  Of  the  fossil  forms,  Hymenocaris  was  regarded  by 
Salter  as  the  more  generalized  type.  The  genera  PeUocaris 
and  Discinocaris  characterize  the  Lower  Silurian  period  ; 
Ceratiocaris  the  upper  ;  Dictyocaris  the  Upper  Silurian  and 
Lowest  Devonian  strata  ;  Dithyrocaris  and  Argus  the  Car- 
boniferous period.  Our  northeastern  and  arctic  species  is 
Nebalia  bipes  (Fabricius),  which  occurs  from  Maine  to  Green- 
land. 

Order  6.  Stomapoda.  In  the  small  group  represented  by 
Squilla  the  gills  are  attached  to  the  base  of  the  hinder  ab- 
dominal feet.  Squilla  lives  in  holes  below  low-water  mark. 

Order  7.  Decapoda  (Shrimps,  Lobsters,  Crabs). — A  gen- 
eral knowedge  of  the  Crustacea  representing  this,  the  high- 
est order  of  the  class,  may  be  obtained  by  a  study  of 
the  craw-fish  and  lobster.  All  Decapods  have  twenty  seg- 
ments in  the  body,  a  carapace  covering  the  thorax  and  con- 
cealing the  gills,  which  are  highly  specialized  and  attached 
to  the  maxillipedes  and  to  the  legs  ;  usually  a  pair  of  stalked 
eyes,  two  unequal  pairs  of  antennae,  the  hinder  pair  the 
larger  and  longer  ;  a  pair  of  mandibles,  often  provided  with 
a  palpus,  two  pairs  of  lobed  maxillae,  three  pairs  of  maxilli- 
pedes, while  the  name  of  the  order  is  derived  from  the  fact 
that  there  are  five  pairs  of  well-marked  legs,  or  ten  in  all. 
To  the  abdomen  are  appended  six  pairs  of  swimming  feet, 
called  "swimmerets."  Another  distinctive  characteristic  of 
most,  in  fact  all  the  higher  Decapods,  is  the  short,  or  five 
or  six-sided  heart. 

The  early  phases  of  embryological  development  in  the  De- 
capods are  much  as  in  the  Tetradecapods.  Most  Decapods 
leave  the  egg  in  a  larval  state  called  the  Zoea.  Certain 
Zoeae  having  originally  been  supposed  to  have  been  adult 
Crustaceans,  were  described  under  the  name  Zoea.  In  this 
condition  there  are  no  thoracic  feet,  and  usually  at  first  no 


DECAPODA.  313 

abdominal  feet;  the  compound  eyes  are  large  and  usually 
sessile,  and  the  carapace  is  often  armed  with  a  long  dorsal 
and  frontal  spine.  Fig.  265  represents  the  Zoea,  or  larva  of 
the  common  shore  crab  (Cancer  irroratus  Say).  After  sev- 


Fig.  265. — Zoea  of  the  common  Crab.    Cancer.    Much  enlarged. — After  Smith. 

eral  moults,  the  thoracic  legs  appear,  the  mouth -parts 
change  from  swimming  -  legs  to  appendages  fitted  for  pre- 
paring the  food  to  be  swallowed  and  digested.  This  stage 
in  the  short-tailed  Decapods  or  crabs,  is  called  the  Mega- 
lops  stage  (Fig.  266);  certain  immature  crabs  having  been 
mistaken  for  and  described  as  mature  Crustacea,  under  the 
name  Megalops.  After  swimming  about  the  surface  in  the 
Zoea  and  Megalops  conditions,  the  body  becomes  more  bulky, 
more  concentrated  headwards,  and  the  crab  descends  to  the 
bottom  and  hides  under  stones,  etc. 

The  development  of  the  individual  crab  is,  in  a  general 
sense,  an  epitome  of  the  development  of  the  order.  In  the 
lowest  Decapods,  as  in  Ouma  and  Mysis,  the  form  is  some- 
what like  an  advanced  Zoea,  while  the  remarkable  concentra- 
tion of  the  parts  headwards,  seen  in  the  crabs,  is  a  great 


314 


ZOOLOGY. 


step  upwards.     Dana's  law  of  cephalization,  or  transfer  of 
parts  headwards,  is  more  strikingly  manifested  in  the  Crus- ' 
tacea  than  in  any  other  animals. 

Nearly  all  Decapods  undergo  this  decided  metamorphosis  ; 
in  only  a  few  forms,  such  as  the  craw-fish,  lobster,  and  a  few 
shrimps  and  crabs,  do  the  young  leave  the  egg  in  the  general 

form  of  the  adult,  the 
Zoe'a  stage  being  rap- 
idly assumed  and  dis- 
carded during  em- 
bryonic life.  Most 
Crustacea  bear  their 
eggs  about  with 
them  ;  in  only  a  few 
cases,  as  the  Squilla 
and  the  land-crab  of 
the  West  Indies,  are 
the  eggs  left  by  the 
parent  in  holes  or  on 
the  sea-shore. 

The  Decapoda  are 
divided  into  the 
Schizopoda,  repre- 
sented by  My  sis  j 
the  Cumacea,  repre- 
sented by  Cuma  ;  the 
long-tailed  Decapods, 
such  as  the  shrimps 
and  lobster,  called 
Macrura,  and  the  genuine  short-tailed  Decapoda,  or  Bra- 
chyura.  Most  of  the  species  of  the  crabs  are  confined  to 
tropical  seas  and  live  in  shallow  water. 

The  Decapods  appeared  in  the  Coal  Period,  and  were  rep- 
resented by  somewhat  generalized  forms,  such  as  AntJira- 
palcemon  (Fig.  267)  from  the  coal  measures  of  Illinois. 
Eecently  a  genuine  crab  (BracJiypyge  carlonis)  has  been 
described  by  "Woodward  from  the  carboniferous  formation 
of  Belgium. 

Crustacea,  especially  shrimps  and  crabs,  are  sensitive  to 


Pig.  266.— Megalops  of  the  Crab.— After  Smith. 


FOtiSIL  CRABS. 


315 


shocks  and  sounds.  When  alarmed,  lobsters  are  said  to 
cast  off  their  large  claws,  but  the  latter  are  again  re- 
newed. It  is  more  probable,  however,  that  the  claws  are 
torn  off  during  their  contests  with  each  other.  Hensen 
found  that  crabs  and  shrimps  liv- 
ing in  water  do  no!  notice  sounds 
made  in  the  air.  The  hairs  about 
the  mouth  are  the  organs  of  tac- 
tile sense,  and  have  been  made  by 
Hensen  to  vibrate  to  certain  sounds. 
The  eyes  may  be  greatly  devel- 
oped in  shrimps  living  at  great 
depths ;  thus  Thalascaris,  a  shrimp 
living  near  the  bottom  of  the  At- 
lantic Ocean,  is  remarkable  for  the 
large  size  of  its  eyes.  In  the  spe- 
cies of  Alpheus,  which  live  in  holes 
in  sponges,  etc.,  the  eves  are  small.  m 

M     1,1.     -i     TT--,  Fig.wr.—Anthrapalcemonara- 

The  eyes  Of  the  blind   WlllemWSia,  <&**.     Natural  size.— After  Meek 
,      ,    J,  ,      ,,        ,  '  and  Worthen. 

dredged  at  great  depths   by  the 

"Challenger"  Expedition,  are  rudimentary,  though  in  the 
young  the  eyes  are  better  developed.  This  is  the  case  with 
the  young  of  the  blind  craw-fish  Cam barus  pellucidus  (Tell- 
kampf,  Fig,  268)  of  Mammoth  and  other  caves.  The  fact 
that  the  eyes  in  the  young  are  larger  than  in  the  adult  indi- 
cates that  this  species  has  descended  from  other  forms  living 
in  neighboring  streams,  and  well  endowed  with  the  sense 
of  sight.  The  eye  (Fig.  269)  of  the  blind  craw-fish  differs 
from  that  of  the  normal  species  in  its  smaller  size,  conical 
form,  the  absence  of  a  cornea  (indicated  by  the  dotted  lines 
in  A),  the  pigment  cells  being  white  instead  of  black,  and 
by  differences  in  the  form  of  the  brain,  that  of  the  blind 
species  being  fuller  on  the  sides,  and  wanting  the  conical 
projection  in  front. 

Sulclass  2.  Palceocarida.—This  subclass  is  proposed  for 
the  king-crab  (Limulus),  the  only  survivor  of  a  large  num- 
ber of  fossil  Crustacea,  which  dominated  the  Silurian  seas 
and  became  mostly  extinct  in  the  Carboniferous  period. 


316 


ZOOLOGY. 


It  comprises  the  order  of  Merostomata  represented  at  the 
present  day  by  the  king-crab,  and  the  order  Trilobita,  which 
is  wholly  extinct.  The  organization  of  the  king-crab  is  so 


Pig.  268.— Cambarus  pellucidus,  the  blind  craw-fish  of  Mammoth  Cave.    Natural 
size. 

wholly  unlike  that  of  other  Crustacea,  when  we  consider 
the  want  of  antennae,  the  fact  that  the  nervous  system  is 


PAL^EOCARIDA. 


317 


peculiar  in  form  and  also  ensheathed  by  arteries,  and  the 
peculiar  nature  of  the  gills  of  the  abdominal  feet,  as  well  as 
the  highly  developed  system  of  blood-vessels  ;  that  we  are 
obliged  to  place  them  in  a  subclass  equivalent  to  all  the  other 


Pig.  269.—  A,  Brain  and  eye  of  a  normal  Cambarus  from  Iowa. 

5,  The  same  of  the  blind  craw-fish  from  Mammoth  Cave. 
(7,  Cornea.— Packard,  del. 

Crustacea.  It  is  possible  that  future  research  may  prove  that 
the  Palceocarida  should  form  a  distinct  class  of  Arthropods, 
equivalent  on  the  one  hand  to  the  Crustacea  and  on  the 
other  to  the  Insecta,  but  from  the  fact  that  they  breathe  like 
other  Crustacea  by  external  gills,  we  prefer  to  retain  them 
as  a  subdivision  of  the  class  of  Crustacea. 

Order  1.  Merostomata. — The  only  living  representative  of 
this  order  is  the  king-crab,  belonging  to  the  genus  Limulus, 
represented  in  American  waters  by  Limulus  Polyphemus 
Linn.,  which  ranges  from  Casco  Bay,  Maine,  to  Florida 
and  the  West  Indies. 

The  body  of  the  king-crab  is  very  large,  sometimes  nearly 
two  feet  in  length  ;  it  consists  of  a  cephalo-thorax  composed 
of  six  segments  and  an  abdomen  with  nine  segments,  the 
ninth  (telson)  forming  a  long  spine.  The  cephalo-thorax  is 
broader  than  long,  in  shape  somewhat  like  that  of  Apus, 
with  a  broad  flat  triangular  fold  on  the  under  side.  Above 
are  two  large  lunate  compound  eyes,  near  the  middle  of  the 
head,  but  quite  remote  from  each  other,  and  two  small  com- 
pound eyes  situated  close  together  near  the  front  edge  of  the 
head.  There  are  no  antennae,  and  the  six  pairs  of  append- 


318  ZOOLOGY. 

ages  are  of  uniform  shape  like  legs,  not  like  mandibles  or 
maxillae,  and  are  adapted  for  walking ;  the  feet  are  pro- 
vided with  sharp  teeth  on  the  basal  joint  for  retaining  the 
food.  The  mouth  is  situated  between  the  second  pair;  the 
first  pair  of  legs  are  smaller  than  the  others.  All  end  in 
two  simple  claws,  except  the  sixth  pair,  which  are  armed 
with  several  spatulate  appendages  serving  to  prop  the  crea- 
ture as  it  burrows  into  the  mud.  The  males  differ  from  the 
females  in  the  hand  and  opposing  thumb  of  the  second  pair 
of  feet.  These  cephalo-thoracic  appendages  are  quite  as  dif- 
ferent from  those  of  other  Crustacea  as  those  of  the  mites 
and  spiders,  which  have  a  pair  of  mandibles  and  maxillae, 
the  latter  provided  with  a  palpus.  Appended  to  the  ab- 
domen are  six  pairs  of  broad  swimming  feet,  of  which  the 
second  pair  bear  on  the  under  side  a  set  of  about  one  hundred 
respiratory  leaves  or  plates,  into  which  the  blood  is  sent 
from  the  heart,  passing  around  the  outer  edge  and  return- 
ing around  the  inner  edge.  This  mode  of  respiration  is  like 
that  of  the  Isopods. 

The  alimentary  canal  consists  of  an  oesophagus,  which 
rises  directly  over  the  mouth,  a  stomach  lined  with  rows  of 
large  chitinous  teeth,  with  a  large  conical,  stopper-like  valve 
projecting  into  the  posterior  end  of  the  body  ;  the  intestine 
is  straight,  ending  in  the  base  of  the  abdominal  spine.  The 
liver  is  very  voluminous,  ramifying  throughout  the  cephalo- 
thorax.  The  nervous  system  is  quite  unlike  that  of  other 
Crustacea ;  the  brain  is  situated  on  the  floor  of  the  body  in 
the  same  plane  as  the  rest  of  the  system,  and  sends  a  pair  of 
nerves  to  the  compound  eyes,  a  single  nerve  supplying  the 
ocelli.*  The  feet  are  all  supplied  with  nerves  from  a  thick 
ring  surrounding  the  oesophagus.  The  nerves  to  the  six 
pairs  of  abdominal  legs  are  sent  off  from  the  ventral  cord. 

*  The  nervous  system  of  Limulusisquite  unlike  that  of  the  Scorpion, 
where  the  brain  is  situated  in  the  upper  part  of  the  head  and  supplies 
the  maxillae  with  nerves,  and  is  situated  directly  over  the  infraceso- 
phageal  ganglion  ;  and,  besides,  there  is  no  O3sophageal  ring  as  in 
Limulus,  only  the  two  commissures  connecting  the  brain  with  tho 
infracesophageal  ganglion  as  usual  in  the  Neocarida  and  Arachnida  in 
general. 


ANATOMY  OF  THE  KING-CRAB.  319 

The  heart  is  tubular,  with  eight  pairs  of  valvular  openings 
for  the  return  of  the  venous  blood  which  flows  into  the 
pericardial  sac  from  all  parts  of  the  body  ;  the  arterial  blood 


Fig.  270.— Nervous  and  part  of  the  circulatory  system  of  Limulus  polyphemus,  the 
King-Crab,  a,  vent  ;  ce,  oesophagus  ;  6,  brain ;  o,  nerve  to  the  smaller  eyee  ;  tf,  nerve 
to  the  larger  eyes ;  s,  nerve-ring  around  the  oesophagus.  All  the  nerves  are  surround- 
ed by  an  arterial  coat.— After  Milne  Edwards. 

is  sent  out  from,  the  arteries  branching  from  the  front  end 
of  the  heart  flowing  around, the  upper  side  of  the  edge  of  the 
cephalo-thorax  through  numerous  minute  vessels.  Also  there 
are  a  pair  of  branchial  arteries,  and  two  arteries  in  the  base  of 
the  spine. 


320 


ZOOLOGY. 


The  arrangement  of  the  ventral  system  of  arteries  is  very 
peculiar  and  quite  characteristic  of  this  animal.  The  oeso- 
phageal  nervous  ring,  and  in  fact  the  entire  nervous  cord,  is 
ensheathed  in  a  vascular  coat,  so  that  the  nervous  system 
and  its  branches  are  bathed  by  arterial  blood.  The  veins 
are  better  developed  than  usual ;  there  being  in  the  cephalo- 
thorax  two  large  collective  veins  along  each  side  of  the  in- 
testine. 

Closely  connected  with  the  two  large  collective  veins  are 
two  large  yellowish  glandular  bodies  each  with  four  branches 
extending  up  into  the  dorsal  side  of  the  cephalo-thorax. 
They  are  probably  renal  in  their  nature. 

Both  the  ovaries  and  testes  are  voluminous  glands,  each 
opening  by  two  papillae  on  the  under  side  of  the  first  ab- 
dominal feet.  At  the  time  of  spawning  the  ovary  is  greatly 
distended,  the  branches  filled  with  green  eggs. 

Unlike  most  Crustacea,  the  female  king-crab  buries  her 
eggs  in  the  sand  between  tide-marks,  and  there  leaves  them 
at  the  mercy  of  the  waves,  until  the  young  hatch.  The  eggs 
are  laid  in  the  Northern  States  between  the  end  of  May  and 


FIG.  271. 


FIG.  272. 


Fig.  271.— Embryo  of  King-crab,  enlarged  ;  am,  serous  membrane  ;  cA,  chorion. 
Fig.  272. — The  same,  more  advanced. 

early  in  July,  and  the  young  are  from  a  month  to  six  weeks 
in  hatching. 

After  fertilization  the  yolk  undergoes  total  segmentation, 
much  as  in  spiders  and  the  craw-fish.  When  the  primitive 
disk  is  formed  the  outer  layer  of  blastodermic  cells  peels  off 
soon  after  the  limbs  begin  to  appear,  and  this  constitutes 


EMBRYOLOGY  OF  THE  KING-CRAB. 


321 


the  serous  membrane  (Fig.  271,  am),  which  is  like  that  of 
insects. 

Then  the  limbs  bud  out ;  the  six  pairs  of  cephalic  limbs 
appear  at  once  as  in  Fig.  271.  Soon  after  the  two  basal 
pairs  of  abdominal  leaf-like  feet  arise,  the  abdomen  be- 
comes separated  from  the  front  region  of  the  body,  and 
the  segments  are  indicated  as  in  Fig.  272.  A  later  stage 
(Fig.  273)  is  signalized  by  the  more  highly  developed  dorsal 
portion  of  the  embryo,  an  increase  in  size  of  the  abdomen, 
and  the  appearance  of  nine  distinct  abdominal  segments.  The 
segments  of  the  cephalo-thorax  are  now  very  clearly  defined, 
as  also  the  division  between  the  cephalo-thorax  and  abdomen, 
the  latter  being  now  nearly  as  broad  as  the  cephalo-thorax, 
the  sides  of  which  are  not  spread  out  as  in  a  later  stage. 


Fig.  273. — King-crab  shortly  before  hatching  ;  trilobitic  stage,  enlarged  ;  side  and 
dorsal  view. 


At  this  stage  the  egg-shell  has  split  asunder  and  dropped 
off,  while  the  serous  membrane,  acting  as  a  vicarious  egg- 
shell, has  increased  in  size  to  an  unusual  extent,  several 
times  exceeding  its  original  dimensions  and  filled  with  sea- 
water,  in  which  the  embryo  revolves. 

At  a  little  later  period  the  embryo  throws  off  an  embry- 
onal skin  (amnion),  the  thin  pellicle  floating  about  in  the 
egg.  Still  later  in  the  life  of  the  embryo  the  claws  are  de- 
veloped, an  additional  rudimentary  gill  appears,  and  the 
abdomen  grows  broader  and  larger,  with  the  segments  more 


322 


ZOOLOGY. 


distinct ;  the  heart  also  appears,  being  a  pale  streak  along 
the  middle  of  the  back  extending  from  the  front  edge  of 
the  head  to  the  base  of  the  abdomen. 

Just  before  hatching  the  head-region  spreads  out,  the  ab- 
domen being  a  little  more  than  half  as  wide  as  the  cephalo- 
thorax.  The  two  compound  eyes  and  the  pair  of  ocelli  on 
the  front  edge  of  the  head  are  quite  distinct  ;  the  append- 
ages to  the  gills  appear  on  the  two  anterior  pairs,  and  the 
legs  are  longer. 

The  resemblance  to  a  Trilobite  is  most  remarkable,  as 
seen  in  Fig.  273.  It  now  also  closely  resembles  the  fossil 
king-crabs  of  the  Carboniferous  formation  (Fig.  274,  Prest- 
wichia  rotundatus,  Fig.  275,  Euproops  Dance). 


Fig.  271.— Prestwichia,  natural  size.— 
After  Worthen. 


Fig.  275. — EuproSps,  natural  size. — 
After  Worthen. 


In  about  six  weeks  from  the  time  the  eggs  are  laid  the 
embryo  hatches.  It  now  differs  chiefly  from  the  previous 
stage  in  the  abdomen  being  much  larger,  scarcely  less  in 
size  than  the  cephalo-thorax  ;  in  the  obliteration  of  the  seg- 
ments, except  where  they  are  faintly  indicated  on  the  car- 
diac region  of  the  abdomen,  while  the  gills  are  much  larger 
than  before.  The  abdominal  spine  is  very  rudimentary  ;  it 
forms  the  ninth  abdominal  segment. 

The  reader  may  now  compare  with  our  figures  of  the  re- 


RELATIONSHIP  OF  L1MULUS  TO   TRILOB1TES.    323 

cently  hatched  Limulus  (Fig.  276),  that  of  Barrande's  larva 
of  Trinucleus  ornatus  (Fig.  277,  natural  size  and  enlarged). 
He  will  see  at  a  glance  that  the  young  Trilobite,  born  with- 
out any  true  thoracic  segments,  and  with  the  head  articu- 
lated with  the  abdomen,  closely  resembles  the  young  Limu- 
lus. In  Limulus  no  new  segments  are  added  after  birth  ; 
in  the  Trilobites  the  numerous  thoracic  segments  are  add- 
ed during  successive  moults.  The  Trilobites  thus  pass 
through  a  well-marked  metamorphosis,  though  by  no  means 
so  remarkable  as  that  of  the  Decapods  and  the  Phyllopods. 


Fig.  277.— Larva  of  a  Trilo- 
bite, Trinudeu»  ornatus.— 
After  Barrande. 


Fig.  276.  —Larva  of  the  King-crab. 


The  young  king-crabs  swim  briskly  up  and  down,  skim- 
ming about  on  their  backs  like  Phyllopods,  by  flapping  their 
gills,  not  bending  their  bodies.  In  a  succeeding  moult,  which 
occurs  between  three  and  four  weeks  after  hatching,  the 
abdomen  becomes  smaller  in  proportion  to  the  head,  and  the 
abdominal  spine  is  about  three  times  as  long  as  broad.  At 
this  and  also  in  the  second,  or  succeeding  moult,  which  oc- 
curs about  four  weeks  after  the  first  moult,  the  young  king- 
crab  doubles  in  size.  It  is  probable  that  specimens  an  inch 
long  are  about  a  year  old,  and  it  must  require  several  years 
for  them  to  attain  a  length  of  one  foot. 

The  Limuli  of  the  Solenhofen  slates  (Jurassic)  scarcely 
differed  in  appearance  from  those  of  their  living  descend- 
ants. 

Limulus,  Prestwichia,  Bellinurus,  and  Euproops   form 


324  ZOOLOGY. 

the  representatives  of  the  suborder  Xipliosura.  The  second 
suborder  Eurypterida  is  represented  by  extinct  genera  Ptery- 
gotus,  Eurypterus  and  allies  which  appeared  in  the  upper 
Silurian  Period  and  became  extinct  in  the  Coal  Period.  In 
these  forms  the  cephalothorax  is  small,  flattened  and  nearly 
square,  while  the  abdomen  is  long,  with  twelve  or  thirteen 
segments,  the  last  one  forming  a  spoon-shaped  or  acute 
spine.  The  appendages  of  the  cephalothorax  were  adapted 
for  walking,  one  pair  sometimes  large  and  chelate ;  the 
hinder  pair  paddle-like.  The  gills  were  arranged  like  the 
teeth  in  a  rake,  the  flat  faces  being  fore  and  aft.  While  the 
king-crab  burrows  in  the  mud  and  lives  on  sea-worms,  the 
Eurypterida  probably  swam  near  the  surface,  and  were  more 
predatory  than  the  king-crabs.  The  Merostomata  are  a  gen- 
eralized type,  with  some  resemblances  to  the  Araclinida  as 
well  as  to  the  genuine  Crustacea,  representing  the  larval  or 
Zoea  form  of  the  Decapods. 

Order  2.  TriloUta. — The  members  of  this  group  are  all 
extinct.  The  body  has  a  thick  dense  integument  like  that 
of  Limulus,  and  is  often  variously  ornamented  with  tuber- 
cles and  spines.  The  body  is  divided  into  three  longi- 
tudinal lobes,  the  central  situated  over  the  region  of  the 
heart  as  in  Limulus.  The  body  is  more  specialized  than  in 
the  Merostomata,  being  divided  into  a  true  head  consisting 
of  six  segments  bearing  jointed  appendages,  somewhat  like 
those  of  the  Merostomata,  with  from  two  to  twenty-six  dis- 
tinct thoracic  segments  (probably  bearing  short  jointed  limbs 
not  extending  beyond  the  edge  of  the  body,  which  support- 
ed swimming  and  respiratory  lobes).  The  abdomen  consisted 
of  several  (greatest  number  twenty-eight)  coalesced  segments, 
forming  a  solid  portion  (pygidium),  sometimes  ending  in.  a 
spine,  and  probably  bearing  membranous  swimming  feet. 
The  larval  trilobite  was  like  that  of  a  king-crab,  and  after  a 
number  of  moults  acquired  its  thoracic  segments,  there  being 
a  well-marked  metamorphosis.  The  Trilobites  (Paradoxides, 
Agnostus,  etc.)  appeared  in  the  lowest  Silurian  strata,  cul- 
minated in  the  upper  Silurian,  and  died  out  at  the  close  of 
the  Coal  Period. 


CLASSIFICATION  OF  CRUSTACEA.  325 


CLASS.  I.  CRUSTACEA. 

Arthropods  breathing  by  gills  situated  on  the  legs,  or  respiring  through 
tJie  body-walls.  Body  in  the  higher  forms  divided  into  two  regions,  a 
cepJialo-thorax  and  abdomen.  Two  pairs  of  antenna  ;  mandibles  usu- 
ally with  a  palpus.  Heart  nearly  square,  or  in  the  lower  forms  tubular. 
Often  a  distinct  metamorphosis.  Sexes  distinct,  except  in  a  few  cases 
(certain  barnacles,  etc.}. 

Subclass  1.  Neocarida. — Genuine  Crustacea,  with  two  pairs  of  anten- 
nae; biting  mouth  parts  ;  mostly  modern  types. 

Order  1.  Cirripedia. — Sessile  often  retrograded  ;  antennae  not  devel- 
oped, living  parasitically,  the  appendages  of  the  head  some- 
times forming  net-like  organs.  Young  hatched  in  the  nau- 
plius  state.  Suborder  1. — Rhizocephala  (Sacculina,  Pelto- 
gaster).  Suborder  2. — Genuine  Cirripedia  (Balanus,  Lepas.) 

Order  2.  Entomostraca. — A  cephalo-thorax  developed  ;  mandibles  and 
three  pairs  of  maxillae  ;  five  pairs  of  thoracic  feet,  no  ab- 
dominal feet ;  without  any  gills.  The  parasitic  forms  more 
or  less  modified  in  shape,  with  sucking  mouth-parts  ;  all 
the  young  of  the  nauplius  form.  Suborder  1.  Copepoda 
(Cyclops).  Suborder  2.  Siphonostoma  (Lernaea,  Caligus,  and 
Argulus). 

Order  3.  Branchiopoda.  Thoracic  feet  leaf-like  ;  one  to  three  pairs  of 
maxillae  ;  number  of  body-segments  varying  from  a  few  to 
sixty  ;  cephalo-thorax  often  well  developed,  and  forming  a 
bivalved  shell.  Young  usually  a  Nauplius.  Suborder  1. 
Ostracoda  (Cypris).  Suborder  2.  Cladocera  (Daphnia).  Sub- 
order 3.  Phyllopoda  (Limnadia,  Apus,  Branchipus,  and  Ar- 
temia.) 

Order  4.  Phyllocarida.  — Body  compressed  ;  rostrum  distinct  from  the 
carapace ;  thoracic  feet  leaf-like  ;  no  metamorphosis.  (Ne- 
balia.) 

Order  5. — Tetradecapoda. — No  cephalo-thorax,  thoracic  segments  dis- 
tinct ;  respiration  often  carried  on  by  the  abdominal  feet. 
Suborder  1.  Isopoda  (Idotaea,  Asellus).  Suborder  2.  Am- 
phipoda  (Gammarus). 

Order  6.  Stomapoda. — Abdominal  feet  respiratory.     (Squilla.) 

Order  7.  Decapoda. — Cephalo-thorax  well  marked,  abdomen  often  bent 
beneath  the  cephalo-thorax  ;  breathing  by  gills  attached  to 
the  maxillipedes  and  legs.  Heart  often  nearly  square. 
Usually  a  well-marked  metamorphosis  ;  young  called  a 


ZOOLOGY. 


Zoea.  Suborder  1.  Cumacea  (Cuma).  Suborder  2.  Schiz- 
opoda(Mys\s).  Suborder  3.  Macrura  (Crangon,  Astacus,  Ho- 
marus).  Suborder  4.  Brachyura  (Cancer). 

Subclass  2.  Palceocarida. — Appendages  of  the  ceplialo-thorax  in  the  form 
of  legs,  rather  than  jaws  ;  no  antennae  ;  brain  supplying 
nerves  to  the  eyes  alone ;  nerves  to  the  cephalo-thoracic  ap- 
pendages sent  off  from  an  resopliageal  ring  ;  nervous  system 
ensheathed  by  a  ventral  system  of  arteries;  metamorphosis 
slight.  Sexes  distinct. 

Order  1.  Mero&tomata. — No  distinct  thoracic  segments  and  appendages. 
(Limulus,  Eurypterus.) 

Order  2.  TriloUta. — Numerous  free  thoracic  segments  and  jointed  ap- 
pendages. (Agnostus,  Paradoxides,  Calymene,  Trinucleus, 
Asaphus  ;  all  extinct.) 

CLASSIFICATION  OF  THE   SUBCLASSES  AND  ORDERS  OF  CRUSTACEA. 


NEOCARIDA. 


PALCEOCARIDA  . 


CRUSTACEA. 

Laboratory  Work. — In  dissecting  the  lobster,  the  shell  or  crust  may 
be  removed  by  a  stout  knife  ;  the  whole  dorsal  portion  of  the  cephalo- 
thorax  and  each  segment  behind,  including  the  base  of  the  telson, 
should  be  removed,  care  being  taken  not  to  injure  the  brain,  which  lies 
just  under  the  base  of  the  rostrum.  The  hypodermis,  or  reddish,  mem- 
branous, inner  layer  of  the  integument,  should  then  be  dissected  away, 


GENERAL  CHARACTERS  OF  INSECTS.  327 

exposing  the  heart,  the  stomach,  the  liver,  and  the  large  muscles  of 
the  abdomen.  The  arterial  system  can  be  injected  with  carmine 
through  the  heart,  and  the  finer  arteries  traced  into  the  large  claws 
and  legs.  In  the  crab,  the  entire  upper  side  of  the  carapace  may  be 
removed  by  the  point  of  a  knife.  The  smaller  Crustacea,  especially 
the  water-fleas,  may  be  examined  alive  under  the  microscope  as  trans- 
parent objects.  In  the  larger  forms  the  stomach  may  be  laid  open  by 
the  scissors  in  order  to  study  its  complicated  structure.  The  eyes  of 
the  lobster  should  be  hardened  in  alcohol  and  fine  sections  made  for 
the  microscope.  This  is  an  operation  requiring  much  care  and  expe- 
rience. Experts  in  embryology  have  sliced  the  eggs  of  certain  Crusta- 
cea and  studied  their  embryology  with  great  success. 


CLASS  II. — INSECT  A  (Centipedes,  Mites,  Spiders,    Winged 

Insects). 

General  Characters  of  Insects.— While  in  the  worms 
there  is  no  grouping  of  the  segments  into  regions,  we  have 
seen  that  in  most  Crustacea  there  are  two  assemblages  of 
segments — i.  e.,  a  head-thorax  and  abdomen.  In  the  insects 
there  is  a  step  higher  in  the  scale  of  life,  a  head  is  separated 
from  the  rest  of  the  body,  which  is  divided  into  three 
regions,  the  head,  thorax,  and  hind-body  (abdomen).  More- 
over, the  insects  differ  from  the  Crustacea  in  breathing  by 
internal  air- tubes  which  open  through  breathing-holes 
(spiracles)  in  the  sides  of  the  body.  The  six-footed  insects 
also  have  wings,  and  their  presence  is  correlated  with  a 
differentiation  or  subdivision  of  the  two  hinder  segments 
of  the  thorax  into  numerous  pieces. 

The  number  of  body-segments  in  winged  insects  is  seven- 
teen or  eighteen — i.  e.,  four  in  the  head,  three  in  the  thorax, 
and  ten  or  eleven  in  the  hind-body.  In  spiders  and  mites 
there  are  usually  but  two  segments  in  the  head,  four  in  the 
thorax,  and  a  varying  number  (not  more  than  twelve)  in 
the  abdomen  ;  in  Myriopods  the  number  of  segments  varies 
greatly — i.  e.,  from  ten  to  two  hundred.  The  appendages 
of  the  body  are  jointed,  and  perform  four  different  func- 
tions— i.  e.,  the  antennae  are  sensorial  organs,  the  jaws  and 
maxillae  are  for  seizing  and  chewing  or  sucking  food  ;  the 


328  ZOOLOGY. 

thoracic  appendages  are  for  walking,  and  the  spinnerets 
of  the  spider,  as  well  as  the  sting  or  ovipositor  of  many 
insects,  are  subservient  in  part  to  the  continuance  of  the 
species. 

Of  the  winged  insects  there  are  two  types  :  first,  those  in 
which  the  jaws  and  maxilla?  are  free,  adapted  for  biting,  as 
in  the  locust  or  grasshopper,  and,  second,  those  in  which 
the  jaws  and  maxillae  are  more  or  less  modified  to  suck  or 
lap  up  liquid  food,  as  in  the  butterfly,  bee,  and  bug. 

Nearly  all  insects  undergo  a  metamorphosis,  the  young 
being  called  a  larva  (caterpillar,  grub,  maggot)  ;  the  larva 
transforms  into  a  pupa  (chrysalis),  and  the  pupa  into  the 
adult  (imago). 

In  order  to  obtain  a  knowledge  of  the  structure,  external 
and  internal,  of  insects,  the  student  should  make  a  careful 
study  of  the  anatomy  of  a  locust  or  grasshopper  with  the  aid 
of  the  following  description  ;  and  afterward  rear  from  the 
egg  a  caterpillar  and  watch  the  different  steps  in  its  metamor- 
phosis into  a  pupa  and  adult.  The  knowledge  thus  acquired 
will  be  worth  more  to  the  student  than  a  volume  of  descrip- 
tions. 

On  making  a  superficial  examination  of  the  locust  (Calop- 
tenus  femur -rub-rum,  or  C.  spretus),  its  body  will  be  seen  to 
consist  of  an  external  crust,  or  thick,  hard  integument,  pro- 
tecting the  soft  parts  or  viscera  within.  This  integument 
is  at  intervals  segmented  or  jointed,  the  segments  more  or 
less  like  rings,  which,  in  turn,  are  subdivided  into  pieces. 
These  segments  are  most  simple  and  easily  comprehended 
in  the  abdomen  or  hind-body,  which  is  composed  of  ten  of 
them.  The  body  consists  of  seventeen  of  these  segments, 
variously  modified  and  more  or  less  imperfect  and  difficult 
to  make  out,  especially  at  each  extremity  of  the  body — 
i.e.,  in  the  head  and  at  the  end  of  the  abdomen.  These 
seventeen  segments,  moreover,  are  grouped  into  three  re- 
gions, four  composing  the  head,  three  the  thorax,  and  ten 
the  hind-body,  or  abdomen.  On  examining  the  abdomen, 
•it  will  be  found  that  the  rings  are  quite  perfect,  and  that 
each  segment  may  be  divided  into  an  upper  (tergal),  a  lateral 
(pleura!),  and  an  under  (sternal)  portion,  or  arc  (Fig.  278,  A). 


ANATOMY  OF  INSECTS. 


329 


These  parts  are  respectively  called  tergite,  pleurite,    and 
sternite,  while  the  upper  region  of  the  body  is  called  the 


Fig.  278.-Exterual  anatomy  of   Caloptenus  spretus,  the  head  and  thorax  disjointed. 
?/p,  uropatagium ;  /,  furcula  :  c,  cercus.— Drawn  by  J.  S.  Kingsley. 

teryum,  the  lateral  the  pleurum,  and  the  ventral  or  under 
portion  the  sternum. 


330  ZOOLOGY. 

As  these  parts  are  less  complicated  in  the  abdomen,  we 
will  first  study  this  region  of  the  body,  and  then  examine  the 
more  complex  thorax  and  head.  The  abdomen  is  a  little 
over  half  as  long  as  the  body,  the  tergum  extending  far 
down  on  the  side  and  merging  into  the  pleurum  without 
any  suture  or  seam.  The  pleurum  is  indicated  by  the  row 
of  spiracles,  which  will  be  noticed  further  on.  The  sternum 
forms  the  ventral  side  of  the  abdomen,  and  meets  the  pleu- 
rum on  the  side  of  the  body. 

In  the  female  (Fig.  278,  B),  the  abdomen  tapers  some- 
what toward  the  end  of  the  body,  to  which  are  appended 
the  two  pairs  of  stout,  hooked  spines,  forming  the  oviposi- 
tor (Fig.  278,  B,  r,  r').  The  anus  is  situated  above  the  upper 
and  larger  pair,  and  the  external  opening  of  the  oviduct, 
which  is  situated  between  the  smaller  and  lower  pair  of 
spines,  and  is  bounded  on  the  ventral  side  by  a  movable  tri- 
angular acute  flap,  the  egg-guide  (Fig.  278,  B,  eg,  and  Fig. 
281). 

The  thorax,  as  seen  in  Fig.  278,  consists  of  three  seg- 
ments, called  the  prothorax,  mesothorax,  and  metathorax,  or 
fore,  middle,  and  hind  thoracic  rings.  They  each  bear  a 
pair  of  legs,  and  the  two  hinder  each  a  pair  of  wings.  The 
upper  portion  (tergum)  of  the  middle  and  hind  segments, 
owing  to  the  presence  of  wings  and  the  necessity  of  freedom 
of  movement  to  the  muscles  of  flight,  are  divided  or  differ- 
entiated into  two  pieces,  the  scutum  and  scutellum*  (Fig. 
278),  the  former  the  larger,  extending  across  the  back,  and 
the  scutellum  a  smaller,  central,  shield-like  piece.  The 
protergum,  or  what  is  usually  in  the  books  called  the  pro- 
thorax,  represents  either  the  scutum  or  both  scutum  and 
scutellum,  the  two  not  being  differentiated. 

The  fore  wings  are  long  and  narrow,  and  thicker  than 
the  hinder,  which  are  broad,  thin,  and  membranous,  and 
most  active  in  flight,  being  folded  up  like  a  fan  when  at 
rest  and  tucked  away  out  of  sight  under  the  fore  wings, 
which  act  as  wing-covers. 

*  There  are  in  many  insects,  as  in  many  Lepidoptera  and  Hymenop- 
tera  and  someNeuropte?'a,  four  tergal  pieces — i.  e.,  praBscutum,  scutum, 
scutellum,  and  postscutellum,  the  first  and  fourth  pieces  being  usually 
very  small  and  often  obsolete. 


ANATOMY  OF  INSECTS. 


331 


332  ZOOLOGY. 

Turning  now  to  the  side  of  the  body  under  the  insertion 
of  the  wing  (Fig.  279),  we  see  that  the  side  of  each  of  the 
middle  and  hind  thoracic  rings  is  composed  of  two  pieces, 
the  anterior,  episternum,  resting  on  the  sternum,  with  the 
epimerum  behind  it  ;  these  pieces  are  vertically  high  and 
narrow,  and  to  them  the  leg  is  inserted  by  three  pieces, 
called  respectively  coxa,  troclmntine,  and  troclianter  (see  Fig. 
279),  the  latter  forming  a  true  joint  of  the  leg. 

The  legs  consist  of  five  well-marked  joints,  the  femur 
(thigh),  tibia  (shank),  and  tarsus  (foot),  the  latter  consist- 
ing in  the  locust  of  three  joints,  the  third  bearing  two  large 
claws  with  a  pad  between  them.  The  hind  legs,  especially 
the  femur  and  tibia,  are  very  large,  adapted  for  hopping. 

The  sternum  is  broad  and  large  in  the  middle  and  hind 
thorax,  but  small  and  obscurely  limited  in  the  pro  thorax, 
with  a  large  conical  projection  between  the  legs. 

The  head  is  mainly  in  the  adult  locust  composed  of  a  sin- 
gle piece  called  the  epicranium  (Figs.  279  and  280,  E),  which 
carries  fche  compound  eyes,  ocelli,  or  simple  eyes  (Fig.  280, 
e),  and  antennae.  While  there  are  in  real- 
ity four  primary  segments  in  the  head  of 
all  winged  insects,  corresponding  to  the 
four  pairs  of  appendages  in  the  head,  the 
posterior  three  segments,  after  early  em- 
bryonic life  in  the  locust,  become  obsolete, 
and  are  mainly  represented  by  their  ap- 
pendages and  by  small  portions  to  which  the 
appendages  are  attached.  The  epicranium 
represents  the  antennal  segment,  and 
mostly  corresponds  to  the  tergum  of  the  seg- 
ment.  The  antennae,  or  feelers,  are  in- 
serted  ^  front  of  the  eyes,  and  between 
mandible;  m«,portion  them  is  the  anterior  ocellus,  or  simple  eye, 

of  maxilla  uncovered  *         J    ' 

by  the  labrum  ;  p,  while  the  two  posterior  ocelli  are  situated 

maxillary  palpns;  jr,       »,-..,.  T 

labial  palpus.—  Kings-  above  the  insertion  of  the  antennae.  In 
front  of  the  epicranium  is  the  clypeus  (Fig. 
280),  a  piece  nearly  twice  as  broad  as  long.  To  the  clypeus 
is  attached  a  loose  flap,  which  covers  the  jaws  when  they 
are  at  rest.  This  is  the  upper  lip  or  labrum  (Fig.  280). 


viewSo?  Sh'ehead  of 


MOUTH-PARTS  OF  INSECTS.  333 

There  are  three  pairs  of  mouth-appendages  :  first,  the  true 
jaws  or  mandibles  (Fig.  278),  which  are  single-jointed,  and 
are  broad,  short,  solid,  with  a  toothed  cutting  and  grinding 
edge,  adapted  for  biting.  The  mandibles  are  situated  on 
each  side  of  the  mouth -opening.  Behind  the  mandibles 
are  the  maxillas  (Fig.  278),  which  are  divided  into  three 
lobes,  the  inner  armed  with  teeth  or  spines,  the  middle  lobe 
unarmed  and  spatula-shaped,  while  the  outer  forms  a  five- 
jointed  feeler  called  the  maxillary  palpus.  The  maxillaa  are 
accessory  jaws,  and  probably  serve  to  hold  and  arrange  the 
food  to  be  ground  by  the  true  jaws.  The  floor  of  the  mouth 
is  formed  by  the  Idbium  (Figs.  278  and  279),  which  in  real- 
ity is  composed  of  the  two  second  maxillae,  soldered  together 

in  the  middle,  the  two  halves  being  drawn  separately  in  Fig. 

2170 
to. 

Within  the  mouth,  and  situated  upon  the  labium,  is  the 
tongue  (lingua),  which  is  a  large,  membranous,  partly  hol- 
low expansion  of  the  base  of  the  labrum  ;  it  is  somewhat 
pyriform,  slightly  keeled  above,  and  covered  with  fine,  stiff 
hairs,  which,  when  magnified,  are  seen  to  be  long,  rough, 
chitinous  spines,  with  one  or  two  slight  points  or  tubercles 
on  the  side.  These  stiff  hairs  probably  serve  to  retain  the 
food  in  the  mouth,  and  are,  apparently,  of  the  same  struc- 
ture as  the  teeth  in  the  crop.  The  base  of  the  tongue  is 
narrow,  and  extends  back  to  near  the  pharynx  (or  entrance 
to  the  gullet),  there  being  on  the  floor  of  the  mouth,  behind 
the  tongue,  two  oblique  slight  ridges,  covered  with  stiff, 
golden  hairs,  like  those  on  the  tongue. 

The  internal  anatomy  may  be  studied  by  removing  the 
dorsal  wall  of  the  body  and  also  by  hardening  the  insect 
several  days  in  alcohol  and  cutting  it  in  two  longitudinally 
by  a  sharp  scalpel. 

The  oesophagus  (Fig.  281,  ce)  is  short  and  curved,  contin- 
uous with  the  roof  of  the  mouth.  There  are  several  longi- 
tudinal irregular  folds  on  the  inner  surface.  It  terminates 
in  the  centre  of  the  head,  directly  under  the  supra-oesopha- 
geal  ganglion,  the  end  being  indicated  by  several  small  coni- 
cal valves  closing  the  passage,  thus  preventing  the  regurgita- 
tion  of  the  food.  The  two  salivary  glands  consist  each  of  a 


ZOOLOGY. 

bunch  of  follicles,  emptying  by  a  common  duct  into  the  floor 
of  the  mouth. 

The  oesophagus  is  succeeded  by  the  crop  (ingluvies).  It 
dilates  rapidly  in  the  head,  and  again  enlarges  before  pass- 
ing out  of  the  head,  and  at  the  point  of  first  expansion  or 
enlargement  there  begins  a  circular  or  oblique  series  of  folds, 
armed  with  a  single  or  two  alternating  rows  of  simple  spine- 
like  teeth.  Just  after  the  crop  leaves  the  head,  the  rugae  or 
folds  become  longitudinal,  the  teeth  arranged  in  rows,  each 
row  formed  of  groups  of  from  three  to  six  teeth,  which 
point  backward  so  as  to  push  the  food  into  the  stomach. 
In  alcoholic  specimens  the  folds  of  the  crop  and  oesophagus 
are  deep  blood-red,  while  the  muscular  portion  is  flesh-col- 
ored. It  is  in  the  crop  that  the  "  molasses  "  thrown  out  by 
the  locust  originates. 

The  proventriculus  is  very  small  in  the  locust,  easily  over- 
looked in  dissection,  while  in  the  green  grasshoppers  it  is 
large  and  armed  with  sharp  teeth.  A  transverse  section  of 
the  crop  of  the  cricket  shows  that  there  are  six  large  irreg- 
ular teeth  armed  with  spines  and  hairs  (Fig.  282).  It 
forms  a  neck  or  constriction  between  the  crop  and  true 
stomach.  It  may  be  studied  by  laying  the  alimentary  canal 
open  with  a  pair  of  fine  scissors,  and  is  then  seen  to  be 
armed  with  six  flat  folds,  suddenly  terminating  posteriorly, 
where  the  true  stomach  (chyle-stomach,  ventriciilus)  begins. 
The  chyle-stomach  is  about  one  half  as  thick  as  the  crop, 
when  the  latter  is  distended  with  food,  and  is  of  nearly  the 
same  diameter  throughout,  being  much  paler  than  the  red- 
dish crop,  and  of  a  flesh-color. 

From  the  anterior  end  arise  six  large  gastric  cwca,  which 
are  dilatations  of  the  true  chyle-stomach,  and  probably  serve 
to  present  a  larger  surface  from  which  the  chyle  may  escape 
into  the  body-cavity  and  mix  with  the  blood,  there  being  in 
insects  no  lacteal  vessels  or  lymphatic  system. 

The  stomach  ends  at  the  posterior  edge  of  the  fourth  ab- 
dominal segment  in  a  slight  constriction,  at  which  point 
(pyloric  end)  the  urinary  tubes  (vasa  urinaria,  Fig.  281, 
ur)  arise.  These  are  arranged  in  ten  groups  of  about  fifteen 
tubes,  so  that  there  are  about  one  hundred  and  fifty  long, 
fine  tubes  in  all. 


ANATOMY  OF  INSECTS. 


335 


Ilplfls. 

tfasftsae.' 


til III! 


336  ZOOLOGY. 

The  intestine  (ileum)  lies  in  the  fifth  and  sixth  abdominal 
segments. 

Behind  the  intestine  is  the  colon,  which  is  smaller  than 
the  intestine  proper,  and  makes  a  partial  twist.  The  colon 
suddenly  expands  into  the  rectum,  with  six  large  rectal 
glands  on  the  inside,  held  in  place  by  six  muscular  bands 
attached  anteriorly  to  the  hinder  end  of  the  colon.  The 
rectum  turns  up  toward  its  end,  and  the  vent  is  situated 
just  below  the  supra-anal  plate. 

Having  described  the  digestive  canal  of  the  locust,  we 
may  state  in  a  summary  way  the  functions  of  the  different 

divisions  of  the  tract.  The 
food  after  being  cut  up  by  the 
jaws  is  acted  upon  while  in 
the  crop  by  the  salivary  fluid, 
which  is  alkaline,  and  pos- 
sesses the  property,  as  in  ver- 
tebrates, of  rapidly  transform- 
ing the  starchy  elements  of 
the  food  into  soluble  and  as- 
similable glucose.  The  diges- 
tive action  carried  on  in  the 
crop  (ingluvies)  then,  in  a  veg- 
etable-feeding insect  like  the 

Fig.  282.— Transverse  section    of    the  locust,  results    in   the     COnver- 
crop  of  Gryllns  cinereus  of  Europe;  muc,      .  «      ,-1  ,         -• 

muscular  walls  ;  r,  horny  ridge  between   SlOn    Ol     tne    Starcny    matters 

into  glucose  or  sugar.     This 

process  goes  on  very  slowly.  When  digestion  in  the  crop 
has  ended,  the  matters  submitted  to  an  energetic  pressure 
by  the  walls  of  the  crop,  which  make  peristaltic  contrac- 
tions, filter  gradually  through  the  short,  small  proventricu- 
lus,  directed  by  the  furrows  and  chitinous  projections  lining 
it.  The  apparatus  of  teeth  does  not  triturate  the  food, 
which  has  been  sufficiently  comminuted  by  the  jaws.  This 
is  proved  by  the  fact,  says  Plateau,  that  the  parcels  of  food 
are  of  the  same  form  and  size  as  those  in  the  crop,  before 
passing  through  the  proventriculus.  The  six  large  lateral 
pouches  (coeca)  emptying  into  the  commencement  of  the 
stomach  (ventriculus)  are  true  glands,  which  secrete  an  al- 


DIGESTION  IN  INSECTS.  337 

kaline  fluid,  probably  aiding  in  digestion.  In  the  stomach 
(ventriculus)  the  portion  of  the  food  which  has  resisted  the 
action  of  the  crop  is  submitted  to  the  action  of  a  neutral  or 
alkaline  liquid,  never  acid,  secreted  by  special  local  glands 
or  by  the  lining  epithelium.  In  the  ileum  and  colon  ac- 
tive absorption  of  the  liquid  portion  of  the  food  takes  place, 
and  the  intestine  proper  (ileum  and  colon)  is  thus  the  seat 
of  the  secondary  digestive  phenomena.  The  reaction  of  the 
secretion  is  neutral  or  alkaline.  The  rectum  is  the  ster- 
coral  reservoir.  It  may  be  empty  or  full  of  liquids,  but 
never  contains  any  gas.  The  liquid  products  secreted  by 
the  urinary  tubes  are  here  accumulated,  and  in  certain  cir- 
cumstances here  deposit  the  calculi  or  crystals  of  oxalic, 
uric,  or  phosphatic  acid.  Insects,  says  Plateau,  have  no 
special  vessel  to  carry  off  the  chyle,  such  as  the  lacteals  or 
lymphatics  of  vertebrates  ;  the  products  of  digestion — viz., 
salts  in  solution,  peptones,  sugar  in  solution,  and  emulsion- 
ized  greasy  matters — pass  through  the  fine  coatings  of  the 
digestive  canal  by  osmosis,  and  mingle  outside  of  this  canal 
with  the  currents  of  blood  which  pass  along  the  ventral  and 
lateral  parts  of  the  body. 

Into  the  pyloric  end  of  the  stomach  empty  the  urinary 
tubes,  their  secretions  passing  into  the  intestine.  These  are 
organs  exclusively  depuratory  and  urinary,  relieving  the 
body  of  the  waste  products.  The  liquid  which  they  secrete 
contains  urea  (?),  uric  acid,  and  urates  in  abundance,  hip- 
puric  acid  (?),  chloride  of  sodium,  phosphates,  carbonate  of 
lime,  oxalate  of  lime  in  quantity,  leucine,  and  coloring  mat- 
ters. 

The  nervous  system  of  the  locust,  as  of  other  insects,  con- 
sists of  a  series  of  nerve-centres,  or  so-called  brains  (ganglia), 
which  are  connected  by  two  cords  (commissures),  the  two 
cords  in  certain  parts  of  the  body  in  some  insects  united  into 
one.  There  are  in  the  locust  ten  ganglia,  two  in  the  head, 
three  in  the  thorax,  and  five  in  the  abdomen.  The  first 
ganglion  is  rather  larger  thjfti  the  others,  and  is  called  the 
"  brain."  The  brain  rests  upon  the  oesophagus,  whence  its 
name,  snpra-cesophageal  ganglion.  From  the  brain  arise  the 
large,  short,  optic  nerves  (Fig.  281,  not  lettered,  but  repre- 


338 


ZOOLOGY. 


sented  by  the  circle  behind  the  brain,  sp  ;   Pig.  283,  op), 
which  go  to  the  compound  eyes,  and  from  the  front  arise 


illiaa 

liny 


Ilifibsf 


•JSS|2§ri 
"8tlN^ 

«=£§•?;§.£• 
_-  2  «  •  =•  d 

2-2  &a.H  f 


182 


the  three  slender  filaments  which  are  sent  to  the  three  ocelli 
(Fig.  281,  oc).     From  immediately  in  front,  low  down,  arise 


NERVOUS  SYSTEM  OF  INSECTS. 


339 


the  anfcennal  nerves  (Fig.  281,  at}.  The  simple  brain  of  the 
locust  may  be  compared  with  the  more  complicated  brain  of 
an  ant,  as  seen  in  Fig.  284. 

The  infra-cesophageal  ganglion  (Fig.  283,  if),  as  its  name 
implies,  lies  under  the  oesophagus  at  the  base  of  the  head,  un- 


aii 


Fig.  284.— Right  half  of  an  ant's-brain:  UG,  infra-cesophageal  ganglion ;  Gr,  brain ; 
C,  central  connective  portions ;  W,  semi-circular  bodies  of  the  small-celled  portion 
of  the  brain  lying  next  to  the  basal  portion  of  the  brain,  from  which  the  nerves  to  the 
pimple  eyes  (an)  arise ;  Au,  optic  lobes ;  An,  antennal  lobes  (the  bodies  appearing 
like  cells  are  rounded  masses  of  the  network  of  the  substance  of  the  cord  ;  r,  cellu- 
lar cortical  substance  of  the  brain ;  ko,  twofold  body  of  the  commissure  connecting 
the  brain  with  the  infra-03sophageal  ganglion.— After  Leydig,  from  Graber. 

der  a  bridge  of  chitine,  and  directly  behind  the  tongue.  It  is 
connected  with  the  supra-oesophageal  ganglion  by  two  com- 
missures passing  up  each  side  of  the  oesophagus.  From  the 
under  side  of  the  infra-cesophageal  ganglion  arise  three 
pairs  of  nerves,  which  are  distributed  to  the  mandibles, 


340 


ZOOLOGY. 


maxillas,  and  labium.  The  mandibular  nerves  project  for- 
ward and  arise  from  the  anterior  part  of  the  ganglion,  near 
the  origin  of  the  supra-oasophageal  commissures,,  while  the 
maxillary  and  labial  nerves  are  directed  downward  into 
those  organs. 

The  sympathetic  ganglia  are  three  in  number  ;  one  situ- 
ated just  behind  the  supra-oasophageal  ganglion  (Fig.  278, 
as),  resting  on  the  ossophagus,  and  two  others  situated  each 
side  of  the  crop,  low  down.  Each  of 
the  two  posterior  ganglia  is  supplied 
by  a  nerve  from  the  anterior  ganglion. 
Two  nerves  pass  under  the  crop  con- 
necting the  posterior  ganglia,  and 
from  each  posterior  ganglion  a  nerve 
is  sent  backward  to  the  end  of  the 
proventriculus.  A  pair  of  nerves  pass 
under  the  oesophagus  from  each  side 
of  the  anterior  sympathetic  ganglion, 
and  another  pair  pass  downward  to  a 
round  white  body,  whose  nature  is 
unknown  (Fig.  278,  u}. 

Fig.  280  represents  an  enlarged 
view  of  the  brain  and  sympathetic 
nerve  of  a  moth.  The  heart  is  a  long 
tube  lying  in  the  abdomen,  dilating 
at  six  places  along  its  course,  and 
ending  in  a  conical  point  near  the 
end  of  the  abdomen  ;  it  is  held  in 
place  by  fine  muscular  bands. 

All  insects  breathe  by  means  of  a 
complicated  system  of  air-tubes  rami- 
fying throughout  the  body,  the  air 
entering  through  a  row  of  spiracles,  or  air-holes,  or  breath- 
ing-holes (stigmata),  in  the  sides  of  the  body.  There  are  in 
locusts  two  pairs  of  thoracic  and  eight  pairs  of  abdominal 
spiracles.  The  first  thoracic  pair  (Fig.  281)  is  situated  on 
the  membrane  connecting  the  pro  thorax  and  mesothorax, 
and  is  covered  by  the  hinder  edge  of  the  protergum  (usually 
called  prothorax).  The  second  spiracle  is  situated  on  the 


Fig.  280.  —  Supra-oesopha- 
geal  ganglion  and  visceral  (or 
sympathetic)  nervous  system 
of  the  Bilk-worm  moth  (Bom- 
byx  mori).  gs,  Supra-oeso- 
phageal  ganglion  (•'  brain'1) ; 
a,  antennary  nerve  ;  0,  optic 
nerve ;  r,  azygos  trunk  of  the 
visceral  nervous  system  ;  r', 
its  roots  arising  from  the 
eupra-oesophageal  ganglion  ; 
f,  paired  nerve  with  its  gangli- 
onic  enlargements  s'  s". — 
After  Brandt,  from  Gegen- 
baur. 


RESPIRATORY  ORGANS  OF  INSECTS.  341 

posterior  edge  of  the  mesothorax.  There  are  eight  abdominal 
spiracles,  the  first  one  situated  just  in  front  of  the  auditory 
sac  or  tympanum  (see  Fig.  279),  and  the  remaining  seven  are 
small  openings  along  the  side  of  the  abdomen,  as  indicated 
in  Fig.  286.  From  these  spiracles  air- tubes  pass  in  a  short 
distance  and  connect  on  each  side  of  the  body  with  the  spi- 
racular  trachea  (Fig.  286,  s,  Fig.  287,  s)  as  we  may  call  it. 
The  air-tubes  consist  of  two  coats,  with  several  short  spiral 
threads  wound  around  the  tube  (Fig.  288).  These  spiracu- 
lar  tracheae  begin  at  the  posterior  spiracle,  and  extend  for- 
ward into  the  mesothorax,  there  subdividing  into  several 
branches.  Branches  from  them  pass  to  the  two  main  ven- 
tral tracheae  (Fig.  286,  v),  and  to  the  two  main  dorsal  tra- 
chea (Fig.  286,  D,  Fig.  287,  D).  The  main  tracheal  sys- 
tem in  the  abdomen,  then,  consists  of  six  tubes,  three  on  a 
side,  extending  along  the  abdomen.  The  pair  of  ventral 
tracheae  extend  along  the  under  side  of  the  digestive  canal ; 
the  dorsal  tracheae  rest  on  the  digestive  canal.  These  six 
tubes  are  connected  by  anastomosing  tracheae,  and,  with 
their  numerous  subdivisions  and  minute  twigs  and  the  sys- 
tem of  dilated  tracheae  or  air- sacs,  an  intricate  network  of 
tracheae  is  formed. 

The  system  of  thoracic  air-tubes  is  quite  independent  of 
the  abdominal  system,  and  not  so  easy  to  make  out.  The 
tubes  arising  from  the  two  thoracic  stigmata  are  not  very 
well  marked  ;  they,  however,  send  two  well-marked  tracheae 
into  the  head  (Fig.  286,  c,  Fig.  287,  c),  which  subdivide  into 
the  ocular  dilated  air-tube  (Fig.  286,  oc,  Fig.  287,  oc)  and  a 
number  of  air- sacs  in  the  front  of  the  head. 

The  series  of  large  abdominal  air-sacs,  of  which  there 
are  five  pairs  (Fig.  287,  3-7),  arise  independently  of  the  main 
tracheae  directly  from  branches  originating  from  the  spira- 
cles, as  seen  in  Fig.  286.  They  are  large  and  easily  found 
by  raising  the  integument  of  the  back.  There  is  a  large 
pair  in  the  mesothorax  (Fig.  287,  2)  and  two  enormous  sacs 
in  the  prothorax  (Fig.  287,  1),  sometimes  extending  as  far 
back  as  the  anterior  edge  of  the  mesothorax.  All  these  sacs 
are  superficial,  lying  next  to  the  hypodermis  or  inner  layer 
of  the  integument,  while  the  smaller  ones  are,  in  many  cases, 


342 


ZOOLOGY. 


S- 


FIQ.  286. 


RESPIRATION  IN  INSECTS.  343 

buried  among  the  muscles.  Besides  the  ordinary  air- sacs, 
there  is  in  the  end  of  the  abdomen,  behind  the  ovaries,  a 
plexus  of  six  dilated  air-sacs  (Fig.  287,  I,  II,  III),  which 
are  long,  spindle-shaped,  and  are  easily  detected  in  dis- 
secting. 

There  is  a  system  of  dilated  tracheae  and  about  fifty  air- 
sacs  in  the  head. 

In  the  legs  two  tracheae  pass  down  each  side  of  the  femora, 
sending  off  at  quite  regular  intervals  numerous  much-branch- 
ing, transverse  twigs  ;  there  is  one  large  and  a  very  small 
trachea  in  the  tibia,  and  the  main  one  extends  to  the  ex- 
tremity of  the  last  tarsal  joint. 

By  holding  the  red-legged  locust  in  the  hand,  one  may 
observe  the  mode  of  breathing.  During  this  act  the  por- 
tion of  the  side  of  the  body  between  the  spiracle  and  the 
pleurum  (Fig.  278,  A)  contracts  and  expands  ;  the  contrac- 
tion of  this  region  causes  the  spiracles  to  open.  The  gen- 
eral movement  is  caused  by  the  sternal  moving  much  more 
decidedly  than  the  tergal  portion  of  the  abdomen.  When 
the  pleural  portion  of  the  abdomen  is  forced  out,  the  soft 
pleural  membranous  region  under  the  fore  and  hind  wings 
contracts,  as  does  the  tympanum  and  the  membranous  por- 
tions at  the  base  of  the  hind  legs.  When  the  tergum  or 
dorsal  portion  of  the  abdomen  falls  and  the  pleurum  con- 
tracts, the  spiracles  open  ;  their  opening  is  nearly  but  not 
always  exactly  co-ordinated  with  the  contractions  of  the 
pleurum,  but  as  a  rule  they  are.  There  were  sixty-five  con- 
tractions in  a  minute  in  a  locust  which  had  been  held  be- 
tween the  fingers  about  ten  minutes.  It  was  noticed  that 
when  the  abdomen  expanded,  the  air-sacs  in  the  first  ab- 

Fig.  286. — Showing  distribution  of  air-tubes  (tncheae)  and  nir-sacs — side  view  of 
the  oody.  v,  main  ventral  trachea  (only  one  of  thu  two  shown) ;  *,  left  stigmatal 
trachea,  connecting  by  vertical  branches  with  D,  the  left  main  dorsal  trachea;  c,  left 
cephalic  trachea  ;  oc,  ocular  dilated  trachea.  From  the  first,  second,  third,  and  fourth 
spiracles  arise  the  first  four  abdominal  air-pace,  which  are  succeeded  by  the  plexus 
of  three  pairs  of  dilated  tracheae,  I,  II,  III,  in  Fig.  287.  Numerous  air-sacs  and 
tracheae  are  represented  in  the  head  and  thorax.  The  two  thoracic  spiracles  are  rep- 
resented, but  not  lettered. 

Fig.  287— D,  left  dorsal  trachea;  S,  left  stigmata!  trachea  ;  T,  II,  III,  first,  second, 
and  third  pairs  of  abdominal  dilated  trachea?,  forming  a  plexus  behind  the  ovaries- 
1,  pair  of  enormous  thoracic  air-sacs  ;  2,  pair  of  smaller  air-sacs ;  3-7.  abdominal 
air-sacs;  oc,  ocular  dilated  trachea  and  air-sacs-  c,  cephalic  trachea.  The  relations 
of  the  heart  to  the  dorsal  tracheae  are  indicated.— Drawn  by  Emerton  from  dissec- 
tions by  the  author. 


344  ZOOLOGY. 

dominal  ring  contracted.  This  would  indicate  that  the 
air  rushes  into  the  spiracles  during  the  contraction  of  the 
abdomen,  and  that  the  air-sacs  are  not  refilled  until  the 
spiracles  are  closed  ;  thus  the  air  in  the  air-sacs  is  perhaps 
constantly  changing. 

It  is  evident  that  the  enprmous  powers  of 
flight  possessed  by  the  locust,  especially  its  fac- 
ulty of  sailing  for  many  hours  in  the  air,  is  due 
to  the  presence  of  these  air-sacs,  which  float  it 
up  in  the  atmospheric  sea.  Other  insects  with 
a  powerful  flight,  as  the  bees  and  flies,  have  well- 
developed  air-sacs,  but  they  are  less  numerous. 
It  will  be  seen  that,  once  having  taken  flight, 
the  locust  can  buoy  itself  up  in  the  air,  con- 
stantly filling  and  refilling  its  internal  buoys  or 
balloons  without  any  muscular  exertion,  and 
thus  be  borne  along  by  favorable  winds  to  its 
destination.  It  is  evident  that  the  process  of 

.—  * 

respira^ion  can  be  best  carried  on  in  clear,  sunny 
trachea  of  Hy-  weather,  and  that  when  the  sun  sets,   or   the 

drophiluspiceus  ,V         .  •    ,        i  T    -,  .",  »  n-    i  i 

or  water-beetle,  weather  is  cloudy  and  damp,  its  powers  01  night 

en,  epithelium;  ,  -,  .  , ,        n .      .     .   ,      -,  » 

cu:  cuticuia ;/,  are  lessened,  owing  to  the  diminished  power  of 
-Afte/Mfnot8'  respiration.  The  finer  structure  of  the  trachea 
is  seen  in  Fig.  288. 

It  is  difficult  to  explain  many  of  the  actions  of  insects, 
from  the  fact  that  it  is  hard  for  us  to  appreciate  their  men- 
tal powers,  instincts,  and  general  intelligence.  That  they 
have  sufficient  intellectual  powers  to  enable  them  to  main- 
tain their  existence  may  be  regarded  as  an  axiom.  But  in- 
sects differ  much  in  intelligence  and  also  in  the  degree  of 
perfection  of  the  organs  of  sense.  The  intelligence  of  in- 
sects depends,  of  course,  largely  on  the  development  of  the 
organs  of  special  sense. 

The  sense  of  sight  must  be  well  developed  in  the  locust, 
there  being  two  large,  well-developed  compound  eyes,  and 
three  simple  ones  (ocelli),  situated  between  the  former,  sup- 
plied with  nerves  of  special  sense. 

Fig.  289  represents  the  eye  of  a  moth  greatly  enlarged  to 
show  the  finer  structure. 


SENSJS8  OF  INSECTS. 


345 


The  antennae  are,  in  the  locust,  organs  of  touch.  The 
palpi  are  not  only  organs  of  touch,  but  probably,  as  in  some 
other  insects,  are  endowed  with  the  sense  of  taste,  enabling 
the  locust  to  discriminate  between  the  different  kinds  of 
food,  and  select  that  best  adapted  to  suit  its  wants.  It  is 
possible  that  the  labial  nerves  send  branches  of  special  sense 
to  the  tongue. 


f -, 


Fig.  289. -Longitudinal  section  of  the  facetted  eye  of  a  moth  :  the  eye-capsnie  or 
sclera  facetted  externally  (/),  and  sieve-like  within,  shows  the  rod-like  ending  of  the 
optic  nerve-fibres  ;  k,  layer  of  the  crystalline  lens;  i,  iris-hke-pigment  zone  •  c/t, 
choroid  composed  of  pigment  cells  ;  sn,  optic  nerve  ;  tr,  trachea  lost  in  fine  bundles 
of  fibrillse.—  After  Leydig,  from  Graber. 

The  ears  are  well  developed  in  the  locust,  and  we  know 
that  the  sense  of  hearing  must  be  delicate,  not  only  from  the 
fact  that  a  loud  alarum  with  kettles  and  pans  affects  them, 
but  the  movements  of  persons  walking  through  the  grass 
invariably  disturb  them.  Besides  this,  they  produce  a  fid- 
dling or  stridulating  sound  by  rubbing  their  hind  legs 
against  their  folded  wing-covers,  and  this  noise  is  a  sexual 


346 


ZOOLOG  Y. 


sound,  heard  and  appreciated  by  individuals  of  the  other 
sex.    Any  insect  which  produces  a  sound  must  be  supposed  to 

have  ears  to  hear  the  sound  pro- 
duced by  others  of  its  species. 
In  the  antennae,  palpi,  and 
abdominal  appendages  of  dif- 
ferent insects  are  seated  mi- 
nute sense  organs  of  unknown 
functions,  though  probably 

either  of  sme11  or  taste  (Fis- 

290). 

The  ears  (or  auditory  sacs)  of  the  locust  are  situated,  one 
on  each  side,  on  the  basal  joint  of  the  abdomen,  just  be- 


Fig.  290.—^!,  b,  sense-organ  on  the  ab 
dominal  appendages  of  a  fly  ( Chrysopila) 


Fig.  291.— Ear  of  a  locust  (Caloptenus  italicus)  seen  from  the  inner  side.  T,  tym- 
panum ;  TE,  its  border  ;  o,  u,  two  horn-like  processes  ;  bi,  pear-shaped  vesicle  ;  n, 
auditory  nerve  ;  ga,  terminal  ganglion;  st,  stigma  ;  m,  opening  and  m/  closing  mus- 
cle of  the  same  ;  J/,  tensor  muscle  of  the  tympanum-membrane.— After  Graber. 

hind  the  first  abdominal  spiracle  (Fig.  279).  The  ap- 
paratus consists  of  a  tense  membrane,  the  tympanum,  sur- 
rounded by  a  horny  ring  (Fig.  291).  "  On  the  internal  sur- 


ORGANS  OF  HEARING. 


347 


face  of  this  membrane  are  two  horny  processes  (ou\  to  which 
is  attached  an  extremely  delicate  vesicle  (/bi)  filled  with  a 
transparent  fluid,  and  representing  a  membranous  labyrinth. 
This  vesicle  is  in  connection  with  an  auditory  nerve  (ri) 


Fig.  292— A  Carabus  beetle  in  the  act  of  walking  or  running.  Three  legs  (V,  IP, 
Z3),  are  directed  forward,  while  the  others  (E\  X2,  #3),  which  are  directed  back- 
ward toward  the  tai  1,  have  ended  their  activity.  ab,cd,  and  ef  are  curves  described 
by  the  end  of  the  tibia?  and  passing  back  to  the  end  of  the  body;  b  h,  d  i,  and/  a  are 
curves  described  by  the  same  legs  daring  their  passive  change  of  position.— After 
Graber. 

which  arises  from  the  third  thoracic  ganglion,  forms  a  gan- 
glion (go)  upon  the  tympanum,  and  terminates  in  the  im- 
mediate neighborhood  of  the  labyrinth  by  a  collection  of 


348 


ZOOLOGY. 


109 


cuneiform,  staff-like  bodies,  with  very  finely-pointed  ex- 
tremities (primitive  nerve-fibres?),  which,  are  surrounded 
by  loosely  aggregated  ganglionic  globules."  (Siebold's 
Anatomy  of  the  Invertebrates.) 

In  walking,  the  locust,   beetle,   or,  in  fact,  any  insect, 
raises   and   puts  down  its  six  legs  alternately,  as  may  be 

seen  by  observing  the  movements 
of  a  beetle  (Fig.  292).  While  the 
structure  of  the  limb  of  a  ver- 
tebrate and  insect  is  not  homol- 
ogous, yet  the  mechanism  or 
functions  of  the  parts  are  in 
the  main  the  same,  as  indicated 
in  Figs.  293  and  294. 

The  footprints  of  insects  are 
sometimes  left  in  fine  wet  sand 
on  the  banks  of  streams  or  by 
the  seaside. 

In  Fig.  295  the  black  dots 
are  made  by  the  fore,  the  clear 
circle  by  the  middle,  and  the 
black  dashes  by  the  hind  legs 
(Graber). 

The  wings  are  developed  as 
folds  of  the  integument,  and 
strengthened  by  hollow  rods 
called  "  veins  ;"  their  branches 
called  "venures."  There  are 
in  the  wings  of  most  insects 
six  main  veins — i.e.,  the  costal, 
the  subcostal,  median,  subme- 
dian,  internal,  and  anal.  They 
are  hollow  and  usually  contain  an  air-tube,  and  a  nerve 
often  accompanies  the  trachea  in  the  principal  veins.  The 
arterial  blood  from  the  heart  (as  seen  in  the  cockroach  by 
Moseley)  flows  directly  into  the  costal,  subcostal,  median, 
and  submedian  veins  ;  here  it  is  in  part  aerated,  and  returns 
to  the  heart  from  the  hinder  edge  of  the  wings  through  the 
hinder  smaller  branches  and  the  main  trunks  of  the  internal 


Fig.  293.— Section  of  the  fore  leg  of 
a  Stag  beetle,  showing  the  muscles.  8. 
extensor,  B,  flexor  of  the  leg ;  a,  ex- 
tensor ;  6,  flexor  of  the  femur;  o,  femur; 
w,  tibia;/,  tarsus  ;  k,  claw,  109.x,  s, 
extensor,  6,  flexor  of  the  femoro-tibial 
joint,  both  enlarged.— After  Graber. 


FLIGHT  OF  INSECTS. 


349 


and  anal  veins.  So  that  the  wings  of  insects  act  as  lungs 
as  well  as  organs  of  flight.  For  the  latter  purpose,  the 
principal  veins  are  situated  near  the  front  edge  of  the  wing, 


t 


Fig.  294. — Diagram  of  the  knee-joint  of  a  vertebrate  (A)  and  an  insect's  limb  (7?). 
a,  upper,  6,  lower  shank,  united  at  A  by  a  capsular  joint,  at  B  by  a  folding  joint ; 
G?,  extensor  or  lifting  muscle  ;  dl,  flexor  or  lowering  muscle  of  the  lower  jo.nt. 
The  dotted  line  indicates  in  A  the  contour  of  the  leg. — After  Graber. 

called  the  costa,  and  thus  the  wing  is  strengthened  when  the 
most  strain  comes  during  the  beating  of  the  air  in  flight. 

The  wing  of  an  insect  in  making  the  strokes  during  flight 
describes  a  figure  8  in  the  air.     A  fly's  wing 
makes  330  revolutions  in  a  second,  executing 
therefore  660  simple  oscillations. 

The  sexes  are  always  distinct  in  insects,  the 
only  known  exception  being  certain  very  low 
aquatic  Arachnida  called  Tardigrada,  in  which 
both  sexual  glands  occur  in  the  same  indi- 
vidual. The  testes  of  the  common  red- 
legged  locust  form  a  single  mass  of  tubular 
glands,  resting  in  the  upper  side  of  the  third, 
fourth,  and  fifth  segments  of  the  hind  body. 
Figs.  296  and  297  represent  this  structure  in 
other  insects.  The  ovaries  consist  of  two  sets 
of  about  twenty  long  tubes,  within  which  the 
eggs  may  be  found  in  various  stages  of  de- 
velopment. The  eggs  pass  into  two  main 
tubes  which  unite  to  form  the  single  oviduct 
which  lies  on  the  floor  of  the  abdomen. 
Above  the  opening  of  the  oviduct  is  the  sebifio 
gland  and  its  duct.  This  gland  secretes  a  copious  supply  of 
a  sticky  fluid,  which  is,  as  in  many  other  insects,  poured 


racks 


5295.  —  Foot- 


350 


ZOOLOGY. 


out  as  the  eggs  pass  out  of  the  oviduct,  thus  surrounding 
them  with  a  tough  coat. 

The  external  parts  consist  of  the  ovipositor  (Fig.  278,  B, 
and  Fig.  281),  which  is  formed  of  two  pairs  of  spines  (rhab- 
dites)  adapted  for  boring  into  the  earth ;  and  of  the  egg- 
guide  (Figs.  278  and  281,  eg),  a  triangular  flap  guarding  the 
under  side  of  the  opening  of  the  oviduct. 


'--to 


Fig.  296.— Male  sexual  apparatus  of  a  bark-beetle,      aefcfenu ;  "ff,  MminaJ  veekSe 

«/,  vas  deferens  ;  ho,  testis  ;  bl,  seminal  vesicle  ;  ay, 
ductus  ejaculatorius. — After  Graber. 


. 

of  Achtta  'campestris.—Mier 
Gegenbaur. 


There  is  a  remarkable  uniformity  in  the  mode  of  develop- 
ment of  the  winged  insects.  In  general,  after  fertilization 
of  the  egg,  a  few  cells  appear  at  one  end  of  the  egg  ;  these 
multiply,  forming  a  single  layer  around  the  egg,  this  layer 
constituting  the  blastoderm.  This  layer  thickens  on  one 
side  of  the  egg,  forming  a  whitish  patch  called  the  primitive 
streak  or  band.  The  blastoderm  molts, 
sloughing  off  an  outer  layer  of  cells, 
a  new  layer  forming  beneath  ;  the  skin 
thus  thrown  off  is  called  the  serous 
membrane ;  the  second  germ-layer 
(ectoderm)  then  arises,  and  a  second 
Section  of  sphinx  membrane  (called  amnion,  but  not 

embryo,  the  germ  immersed    "hnrnnlnovma  Tuifli    fhaf    r\f   vorf aVkrnfo^ 
in  the  yolk  ;   «,  serous  mem-    1  >K)gOUS  Wltll    tnat    01   VerteDratCSj 


peels  off  from  the  primitive  band  just 
as  the  appendages  are  budding  out,  so 
that  the  body  and  appendages  of  the  embryo  insect  are  en- 
cased in  the  amnion  as  the  hand  and  fingers  are  encased  by 
a  glove.  As  seen  in  the  accompanying  Figs.  298-303,  the 


DEVELOPMENT  OF  INSECTS. 


351 


appendages  bud  out  from  the  under  side  of  the  primitive 
band,  and  antennae,  jaws,  legs,  ovipositor  (or  sting),  and  the 
abdominal  feet  of  caterpillars  are  at 
first  all  alike.  Soon  the  appendages 
begin  to  assume  the  form  seen  in 
the  larva,  and  just  before  the  insect 
hatches  the  last  steps  in  the  elabora- 
tion of  the  larval  form  are  taken. 

As  to  the  development  of  the  in- 
ternal organs,  the  ner- 
vous system  first  origi- 
nates ;  the   alimentary 
canal  is  next  formed  ; 

Fig.  299.—  Embryo  of  Sphinx           ,  ,      ,        ,  ,  ,  .      ,  . 

much  more  advanced,    h,  heart  ;  and  at  about  this  time 

g,   ganglion  ;    i,   intestine  :    m.  xv  >•           i_  T 

rudimentary  muscular  bands  run-  the  Stigmata  and    air- 


•at 


arse  as  nvagna- 
193-296  tionsof  the  outer  germ- 
layer.  The  development 

of  the  salivary  glands  precedes  that  of  the  uri- 
nary tubes,  which,  with  the  genital  glands,  are 
originally  offshoots  of  the  primitive  digestive 
tract.  Finally  the  heart  is  formed. 

When  the  insect  hatches,  it  either  cuts  its  way 
through  the  egg-shell  by  a  temporary  egg-cut- 
ter, as  in  the  flea,  or  the  expansion  of  the 
head  and  thorax  and  the  convulsive  movements 
of  the  body,  as  in  the  grasshopper,  burst  the 
shell  asunder.  The  serous  membrane  is  left  in 
the  shell,  but  in  the  case  of  grasshoppers  the 
larva  on  hatching  is  still  enveloped  in  the  am-  J?gJ®Jts 
nion.  This  is  soon  cast  as  a  thin  pellicle.  their  ™d' 

The  principal  change  from  the  larval  to  the  ages,  c,  upper 

.,,.,  %  •     .1  •   •!•  .e    "P  5  at,  anten- 

adult  locust  or  grasshopper  is  the  acquisition  01  nse  ;  md,  man- 

wings.     In  such  insects,  then,  as  the  Orthoptera 

and  Hemiptera,  in  which  the  adults  differ  from 

the  newly  hatched  larva  mainly  in  the  posses- 

sion  of  wings,  metamorphosis  is  said  to  be  in- 

complete.    In  the  beetle,  butterfly,  or  bee,  the  metamorphosis 

is  complete  ;  the  caterpillar,  for  example,  is  a  biting  insect, 


Fig.  300.— 
Primitive 
band  or  germ 


352 


ZOOLOGY. 


is  voracious,  and  leads  a  different  life  from  the  quiescent, 
sleeping  pupa  or  chrysalis,  which  takes  no  food  ;  on  the 
other  hand,  the  imago  or  butterfly  has  mandibles,  which 
are  rudimentary,  and  incapable  of  biting,  while  the  maxillae, 
or  "tongue,"  which  were  rudimentary  in  the  caterpillar, 
become  now  greatly  developed  ;  and  the  butterfly  takes 


st:ii 


Fig.  801.  — Embryo  of  a 
Water-beetle  (Hydrophilus).  E, 
egg  ;  K,  head  ;  ol,  upper  lip;  m, 
mouth  :  an.  antennae  ;  A;,,  man- 
dibles ;  *„,  *,,  maxillae;  S, 
thorax  ;  *,,  62,  &,,  legs  ;  /fcj-fyo, 
ten  pairs  of  rudimentary  abdo- 
minal legs,  of  which  all  except  ht 
disappear  before  the  insect 
hatches  ;  a,  anus,— After  Kowa- 
levsky. 


Fig.  302.— Profile  view  of  embryo 
Honey-bee,  lettering  as  in  Fig. 
301.  BM<  nervous  cord;  oG,  brain; 
D,  digestive  canal  ;  sch,  the  oeso- 
phagus ;  St,  stigmatal  ojpenings  of 
the  tracheal  system ;  .S,  heart.— 
After  Blutschli. 


liquid  food  and  but  little  of  it,  while  its  surroundings  and 
mode  of  life  are  entirely  changed  with  its  acquisition  of 
wings.  Thus  the  butterfly  leads  three  different  lives,  differ- 
ing greatly  in  structure,  externally  and  internally,  at  these 
three  periods,  and  with  different  environments. 


METAMORPHOSIS  OF  INSECTS. 


353 


Most  caterpillars  moult  four  or  five  times ;  at  each 
moult  the  outer  layer  of  the  skin  is  cast  off,  the  new 
skin  arising  from  the  hypodermis,  or  inner  layer  of  the  in- 
tegument. The  skin  opens  on  the  back  behind  the  head, 
the  caterpillar  drawing  itself  out  of  the  rent.  In  the 
change  from  the  caterpillar  to  the  chrysalis,  there  are  re- 
markable transformations  in  the  muscles,  the  nervous, 
digestive,  and  circulatory  system,  inducing  a  change  of 
form,  external  and  internal,  characterizing  the  different 
stages  in  the  metamorphosis. 

While  the  changes  in  form  are 
comparatively  sudden  in  flies  and 
butterflies,  the  steps  that  lead  to 
them  are  gradual.  How  gradual 
they  are  may  be  seen  by  a  study  of 
the  metamorphosis  of  a  bee.  In 
the  nest  of  the  humble  or  honey 
bee,  the  young  may  be  found  in  all 
stages,  from  the  egg  to  the  pupa 
gayly  colored  and  ready  to  emerge 
from  its  cell.  It  is  difficult  to 
indicate  where  the  chrysalis  stage 
begins  and  the  larva  stage  ends, 
yet  the  metamorphosis  is  more 
complete — namely,  the  adult  bee 
is  more  unlike  the  larva,  than  in 
any  other  insect. 

Besides  the  normal  mode  of  de- 
velopment,  certain  insects,  as  the 
plant-louse  (Aphis),  the  bark-louse  «*,  a^ow18e;  vk  forehead-~~After 
(Coccus),  the  honey-bee,  the  Po- 

listes  wasp,  the  currant  saw-fly  (Nematus),  the  gall-flies, 
and  a  few  others,  produce  young  from  unfertilized  eggs. 
Certain  moths,  as  the  silk-worm  moth  (Bombyx  mori)  and 
others,  have  been  known  to  lay  unfertilized  eggs  from  which 
caterpillars  have  hatched.  This  anomalous  mode  of  repro- 
duction is  called  parthenogenesis,  and  fundamentally  is  only 
a  modification  of  the  mode  of  producing  young  by  budding 
which  is  universal  in  plants,  and  is  not  unusual,  as  we  have 


354  ZOOLOGY. 

seen,  among  the  lower  branches  of  the  animal  kingdom. 
The  object  or  design  in  nature,  at  least  in  the  case  of  the 
plant-lice  and  bark-lice,  as  well  as  the  gall-flies,  is  the  pro- 
duction of  large  numbers  of  individuals,  by  which  the  per- 
petuity of  the  species  is  maintained. 

Insects  are  both  useful  and  injurious  to  vegetation.  Were 
it  not«for  certain  bees  and  moths,  orchids  and  many  other 
plants  would  not  be  fertilized  ;  insects  also  assist  in  the 
cross-fertilization  of  plants.  For  full  crops  of  many  of  our 
fruits  and  vegetables,  we  are  largely  indebted  to  bees,  flies, 
moths,  and  beetles,  which,  conveying  pollen  from  flower  to 
flower,  ensure  the  production  of  abundant  seeds  and  fruits. 
Mankind,  on  the  other  hand,  suffers  enormous  losses  from 
the  attacks  of  injurious  insects.  Within  a  period  of  four 
years,  the  Rocky  Mountain  locust,  migrating  eastward,  in- 
flicted a  loss  of  $200,000,000  on  the  farmers  of  the  West. 
In  the  year  1864,  the  losses  occasioned  by  the  chinch-bug  in 
the  corn  and -wheat  crop  of  the  valley  of  the  Mississippi 
amounted  to  upward  of  $100,000,000.  It  is  estimated  that 
the  average  annual  losses  in  the  United  States  from  insects 
are  about  $100,000,000.  On  the  other  hand,  hosts  of 
ichneumon  flies  and  Tachina  flies  reduce  the  numbers  and 
prevent  undue  increase  in  the  numbers  of  injurious  insects. 

The  number  of  species  of  insects  is  estimated  to  be  about 
190,000.  Of  these  there  are  about  25,000  species  of  Hyme- 
noptera  (bees,  wasps,  etc.)  ;  about  25,000  species  of  Lepi- 
doptera  (butterflies  and  moths)  ;  about  24,000  Diptera  (two- 
winged  flies),  and  90,000  Coleoptera  (beetles)  ;  with  about 
4600  species  of  Arachnida  (spiders,  etc.),  and  800  species 
of  Myriopoda  (millepedes,  centipedes,  etc.) 

Insects  are  distributed  all  over  the  surface  of  the  earth. 
Most  of  the  species  are  confined  to  the  warmer  portions  of 
the  globe,  becoming  fewer  in  the  number  of  species  as  we 
approach  the  North  Polar  regions.  Many  are  inhabitants 
of  fresh  water ;  a  very  few  inhabit  the  sea. 

Insects,  so  far  as  the  records  go,  first  appeared  in  the 
Devonian  rocks  ;  these  were  Neuroptera  and  Orthoptera,  such 
as  May-flies  and  other  forms  which  seem  generalized  in 
their  structure.  But  if  highly  developed  flying  insects,  be- 


PERIPATUS.  .  355 

longing,  at  least  the  May-fly,  to  existing  families,  appeared 
in  the  Devonian  period,  it  is  reasonable  to  suppose  that  in- 
sects must  have  inhabited  the  dry  land  of  the  Silurian 
period. 

Insects  are  divided  into  four  sub-divisions  or  sub-classes — 
i.e.,  the  Malacopoda,  the  Myriopoda,  the  Arachnida,  and 
the  six-footed,  winged  insects,  or  Hexapoda.  All  agree  in 
breathing  by  air- tubes,  and  in  having  in  most  cases  a  tri- 
regional  arrangement  of  the  segments  of  the  body.  By  some 
authors  the  three  higher  groups  are  regarded  as  independent 
classes,  but  they  are  all  modifications  of  a  general  insect 
form,  with  similar  mouth-parts,  a  single  pair  of  antennae, 
when  these  organs  are  present,  with  no  palpus  to  the  man- 
dibles, and  with  other  characters  which  render  the  class 
Insecta  equivalent  to  the  class  Crustacea. 

Sub-class  1.  Malacopoda. — This  group  is  represented  by 
a  single  animal,  the  strange  Peripatus  of  tropical  coun- 
tries, in  which  the  body  is  cylindrical,  the  integument,  an- 
tennae, and  limbs  soft,  not  chitinized,  with  the  head  not 
separate  from  the  body,  and  bearing  a  pair  of  many-jointed 
extensible  antennae,  with  two  pairs  of  rudimentary  jaws 
(mandibles  and  maxillae),  and  from  fourteen  to  thirty-three 
pairs  of  feet  (according  to  the  species).  This  animal  differs 
from  other  Arthropods  in  the  two  widely  separated  minutely 
ganglionated  nervous  cords  sent  backward  from  the  brain ; 
also  in  the  minute,  numerous  tracheal  twigs  arising  from 
numerous  minute  oval  openings  (rudimentary  spiracles) 
situated  irregularly  along  the  median  line  of  the  ventral 
surface  of  the  body.  The  feet  are  soft,  fleshy,  and  end  in 
two  claws.  Peripatus  is  viviparous.  According  to  the 
description  and  figures  of  Mr.  Moseley,  the  young  develop 
much  as  in  the  chilopodous  Myriopods  (Geophilus),  show- 
ing that  Peripatus  is  nearer  to  the  Myriopods  than  any 
other  group.  That  it  is  a  tracheate  animal  was  also  proved 
by  Mr.  Moseley ;  but  owing  to  the  nature  of  the  nervous 
system  and  the  minute  tracheae  and  their  numerous  irregular 
spiracular  openings,  with  no  chitinous  edge,  this  form  cannot 
be  placed  among  the  Myriopods.  On  the  other  hand,  it  has 
some  features  recalling  the  Linyuatulina  and  Tardigrada, 


356  ZOOLOGY. 

as  seen  in  the  soft  clawed  feet  and  short  wrinkled  segments. 
It  is  certainly  not  a  worm,  but,  on  the  whole,  connects  the 
worms  with  the  sucking  Myriopods,  and  suggests  that  the 
insects  may  have  descended  from  forms  somewhat  like  Peri- 
patus. Peripatus  iuliformis  inhabits  the  West  Indies,  and 
either  P.  Edwardsii  Blanchard,  or  an  und  escribed  species 
about  four  centimetres  in  length  (with  twenty-seven  pairs 
of  legs),  inhabits  the  Isthmus  of  Panama.  The  name 
Malacopoda  was  proposed  by  De  Blainville,  who  suggested 
that  Peripatus  connected  the  Myriopods  with  the  Annelids. 
There  is  but  a  single  genus,  Peripatus. 

Sub-class  2 .  Myriopoda. — The  centipedes  an  d  millepedes 
are  distinguished  by  their  cylindrical  body,  the  abdominal 
segments  being  numerous  and  similar  to  the  thoracic  seg- 
ments, all  provided  with  a  pair  of  feet.  The  head  is  free, 
with  a  pair  of  antennae,  mandibles,  and  usually  two  pairs  of 
maxillae.  The  internal  organization  is  simple,  like  that  of 
the  larvae  of  insects.  Some  Scolopendrce  are  said  to  be 
viviparous. 

Order  1.  Chilognatha. — To  this  group  belong  the  mille- 
pedes, Julus,  etc.  (Figs.  304-307).  The  first  maxillae  are 
absent.  The  segments  are  round  or  flattened,  and  the  feet 
are  inserted  near  together,  the  sternum  being  undeveloped. 
In  some  forms  (Fig.  304,  Spirostrephon  Copei  Pack.,  from 
Mammoth  Cave)  the  body  is  hairy.  They  are  all  harmless. 
The  eggs  are  laid  in  large  numbers  an  inch  or  two  beneath 
the  surface  of  the  earth.  They  undergo  total  segmentation, 
and  in  a  few  days  the  larva  (Fig.  305)  hatches.  At  this  time 
it  bears  a  resemblance  to  a  Podura,  having  but  three  pairs 
of  feet,  the  third  pair  attached  to  the  fourth  thoracic  seg- 
ment. After  a  series  of  moults,  new  segments  and  new  feet 
appear,  and  thus  these  Myriopods  undergo  a  distinct  meta- 
morphosis. The  species  feed  on  dead,  sometimes  fresh 
leaves,  and  on  fallen  fruit. 

Order  2.  Pauropoda. — The  two  orders  of  Myriopods  are 
connected  by  Pauropus,  which  by  Lubbock  is  regarded  as 
the  type  of  a  distinct  order  (Pauropoda}.  Our  only  species, 
Pauropus  Lubbockii  Pack.  (Fig.  309),  consists  of  six  seg- 
ments besides  the  head,  and  the  young  Pauropus  has  but 


MTRIOPODS. 


357 


1.— Spiros- 
trephon  copei  of 
Mammoth  Cave. 


Fig.  305.— Larva  of 
Jnlus.  a,  third  ab- 
dominal segment,  with 
the  new  limbs  just 
budding  out;  6,  new 
segments  arising  be- 
tween the  penultimate 
and  the  last  segment.— 
After  Newport. 


—Polydes- 
vnus  ery- 
thropygus 
—common 
Polydes- 
xnus. 


Fig.  307 .—Polydesmua  cavicola,  from  Utah, 
top  and  side  view,  a,  antenna ;  ft,  a  segment 
and  leg:  c,  dorsal  view  of  two  segments  show- 
ing ornamentation  :  d,  side  view  of  two  terminal 
segments  of  the  body— all  magnified. 


Natural  size. 


358 


ZOOLOGY. 


three  pairs  of  feet,  and  in  this  and  other  respects  resembles 
Podura.    A  second  form,  Eurypauropus,  of  Ryder,  has  six 
segments,  with  feet  wholly  concealed  from 
above  by  the  expanded  segments. 

Order  3.  (Jliilopoda. — This  group  is  rep- 
resented by  the  centipede  and  Lithobius, 
in  which  the  body  is  flattened,  the  sternal 
region  being  well  developed.  In  Geophilus 
(Fig.  308,  G.  Upuncticeps  Wood)  and  allies 
there  are  from  thirty  to  two  hundred  seg- 
ments. Our  most  common  form  is  Litlio- 
Mus  Americanus  Newport,  found  under 
logs,  etc.  The  centipede  (Scolopendra 
Jieros  Girard)  is  very  poisonous,  the  poison- 
sac  being  lodged  in  the  two  large  fangs  or 
first  pair  of  legs.  8.  gigantea  Linn.,  of 
the  East  Indies,  is  nine  inches  long.  In 
Cermatia  the  body  is  short,  with  compound 
eyes  in  the  head  and  remarkably  long 
slender  legs.  0.  forceps  Rafinesque,  of  the 
Middle  and  Southern  States,  is  said  to  be 
poisonous. 

An  aberrant,  generalized  form  is  Scolo- 
pendrella,  in  which  the  head  and  antennae  are  like  those  of 
Campodea,  a  Thysanurous  insect ;  this  is  therefore  a  con- 
necting link  between  the  Myriopods  and  Hexapods. 

Sub-class  3.  Arachnida. — The  bodies  of  spiders  and  scor- 
pions, etc.,  are  divided  into  two 
regions,  a  head-thorax  and  abdomen, 
the  head  being  closely  united  with 
the  thorax.  There  are  no  antennae, 
only  a  pair  of  mandibles  and  a  pair 
of  maxillae,  with  four  pairs  of  legs. 
There  are  never  any  compound  eyes. 
The  young  are  usually  like  the  adult, 
except  in  the  mites,  in  which  there 
is  a  slight  metamorphosis.  In  all 


Fig.  3QQ.—Pauropus 
Lvbbockii.  Much  en- 
larged. Fig.  310  en- 
larged view  of  head 
ana  antennse  and  first 
pair  of  feet. 


Fig.  310.— Head  of  Paurojws 
Lubbockii.    Much  enlarged. 


Arachnida  there  is  a  liver,  this  organ  not  being  present  in 
the  winged  insects. 


ANATOMY  OF  THE  SPIDER. 


359 


spW1 


Fig.  311.— Anatomy  of  a  spider,  diagrammatic  longitudinal 
section  through  the  body,  an,  simple  eyes  and  nerves  leading 
to  them  from  the  brain  (supra-cesophageal  ganglion,  oG) ; 
any,  mandibles ;  fa2,  palpus  of  maxilla  J, ;  /2.  flrst  Pair  of  legs, 
6, ~&3,  succeeding  pairs  ;  K,  head  ;  Br,  thorax  ;  /?,  hind-body 
or  abdomen;  ft  if,  heart  or  dorsal  vessel ;  L,  lung  in  front  of 
the  opening  of  the  oviduct  G ;  the  spinning-glands  (sp)  con- 
nect with  the  spinnerets,  sp  W.  The  digestive  tract  is  shaded, 


The  type  of  the  sub-class  is  the  spider,  which  is  character- 
ized by  the  pos- 
session of  two 
or  three  pairs 
of  spinnerets, 
which  are 
jointed  a  p  - 
pendages  ho- 
mologous with 
the  legs.  Be- 
sides tracheae, 
spiders  have  a 
so-called  lung 
(Fig.  311,  L), 
composed  of 

fj*~i/3j  om^ccu.iii^    j/ana  ,    JL\.^  nt'an  ,    -ur?  LII\JIO,A.  ,    L~M.^  iiiiiu.-uuu^ 

or  abdomen;  ft  if,  heart  or  dorsal  ^essel ;  L,  lung  in  front  of    several     leaVCS, 

into  which  the 

and  in  the  abdomen  enveloped  in  the  liver.— After  Graber.         -,   -,          1      fl 

and  is  thus  aerated.    In  Lycosa  the  blood  flows  through  the 

heart  from  the  head  backward.     There  is  a  great  range  of 

structure,  from  the  lowest 

mites  to  the  spiders,  certain 

mites  having  no  heart,  no 

tracheae,  very  rudimentary 

mouth-parts,  and  no  brain, 

there   being   but   a  single 

ganglion  in  the  abdomen. 

Order  1.  Acarina. — The 
mites  are  the  simplest 
Arachnida,  the  body  being 
oval  in  form,  the  head 
usually  small,  more  or  less 
merged  with  the  thorax, 

While  the  latter  is   not  dif-        Fig  ^_Ixod€8  ampictm  from  a  partly 
fprpirHarpfl  frrvm  thp   ahflo      domesticated  moose.    The  tick  natural  size, 

gorged  with  blood,  and  its  six-legged  young, 

men.      There     is     a     Slight    much  enlarged,    o,  beak  or  mandibles  armed 

&.         with  teeth  ;  6,  maxilla,  and  c,  maxillary  pal- 

metamorphoSlS,     the     mite    pus ;  d,  a  foot  with  eucker  and  claws,  en- 

when  first  hatched  having    arged' 

but  three  pairs  of  legs,  the  fourth  (and  last)  pair  being  added 


360 


ZOOLOGY. 


after  a  moult.  A  typical  mite,  though  above  the  average 
size  of  the  members  of  the  group,  is  the  tick  (Fig.  312), 
Ixodes  albipicius  Pack.  Closely  allied  to  this  is  Ixodes  bovis 
Riley,  the  cattle-tick  (Fig.  313),  which  buries  its  head  in 


Fig.  314.— Sugar-mite.    Much  en- 


.  313.— Ixodeabovis.  Natural  size  and 
larged. 


Fig.  315.— Amnwtrhoe,  pycnogonoides.  a, 
stomach  with  cceca  (6,  6,  b,  b)  extending 
into  the  legs.— From  Gegenbaur. 


Fig.    SlQ.—Pentastoma    tcenioides. 
Natural  size.— From  Verrill. 


the  skin,  anchoring  itself  firmly  by  means  of  the  backward  - 
pointing  teeth  of  its  jaws.    Other  examples  of  mites  are  the 
cheese  and  sugar  mites  (Fig.  314,  Tyroglyphus  sacchari). 
The  sea-mites,  Pycnogonidce,  are  marine  forms,  without 


BEAR  ANIMALCULES 


361 


air-tubes,  with  four  pairs  of  long  legs,  into  which  coecal 
prolongations  of  the  stomach  pass,  as  seen  in  Fig.  315. 


tardigradum, 
x  120  times.  /,  mouth-parts  ;  ft,  alimen- 
tary canal ;  ov,  ovary.— After  Doyere. 


Fig.  318.— Carolina  scorpion  (Buthu* 
Carolinianus).   Natural  size. 


The  lowest  mites  comprise  remarkable  worm-like  Acarina, 
called  Linguatulina.  The  young  are  mite-like,  the  body 
spherical,  with  boring  jaws,  and  two 
pairs  of  short-clawed  feet.  Pentas- 
toma  (Fig.  316)  occurs  in  the  lungs 
and  liver  of  man,  and  in  horses  and 
sheep. 

The  Tardigrada  or  bear  animal- 
cules (Fig.  317)  are  a  step  higher 
in  the  scale  of  mite  life.  In  these 
singular  beings  the  sexual  glands 
exist  in  the  same  individual. 

Macrobiotus  Americanus  Packard 
is  common  in  sphagnum  swamps, 
Like  the  Rotatoria,  these  low  mites 
are  capable  of  revivifying  after  being  apparently  dead  and 
dried  up. 


Masnmed- 


362  ZOOLOGY. 

Order  2.  Pedipalpi. — This  group  embraces  the  scorpion 
(Fig.  318),  the  false  scorpions  (Fig.  319),  the  whip  scor- 
pions, and  the  harvest-man  (Phalangium).  In  all  these 
forms  the  abdomen  is  plainly  segmented,  the  segments  not 
being  visible  in  the  mites  or  spiders.  Usually  the  maxillary 
palpi  are  much  enlarged,  and  end  in  claws.  The  scorpion 
is  viviparous,  the  young  being  brought  forth  alive.  The 
young  scorpions  cling  to  the  back  of  the  mother.  The  sting 
of  the  scorpion  is  lodged  in  the  tail,  which  is  perforated, 
and  contains  in  the  bulbous  enlargement  an  active  poison. 
Though  producing  sickness,  pain,  and  swelling  in  the  arm, 
the  sting  of  the  scorpion  is  seldom  fatal. 

The  little  false-scorpions  (Chelifer,  Fig.  319)  of  ten  occur  in 
books,  under  the  bark  of  trees,  and  under  stones.  The  whip- 
scorpion  is  confined  to  warm  countries.  Thelyphonus  gigan- 
teus  Lucas  occurs  in  New  Mexico  and  Mexico.  Its  abdomen 
ends  in  a  long  lash-like  appendage.  Its  bite  is  poisonous. 
The  harvest-men,  or  daddy-long-legs,  are  common  in  dark 
places  about  houses.  They  feed  on  plant-lice.  Our  common 
species  is  Phalangium  dorsatum  Say. 

Order  3.  Araneina. — The  spiders  are  always  recogniza- 
ble by  their  spherical  abdomen,  attached  by  a  slender  pedicel 
to  the  head-thorax.  They  breathe,  like  the  scorpions,  both 
by  lungs  as  well  as  by  tracheae,  and  the  young  resemble  the 
parent  in  having  four  pairs  of  feet. 

The  development  of  the  spider  has  some  peculiarities  not 
found  in  the  higher  insects.  The  egg  undergoes  total  seg- 
mentation. The  germ  is  somewhat  worm-like,  as  in  Fig. 
320,  then,  as  in  (7,  the  primitive  band  forms,  with  head  and 
tail  end  much  alike.  Afterward  (Fig.  321)  the  head  ac- 
celerates in  development,  and  the  appendages  begin  to  bud 
out,  six  pairs  of  abdominal  limbs  appearing  and  then  totally 
disappearing,  except  the  three  pairs  of  spinnerets,  as  if  the 
spiders  were  descended  originally  from  some  Myriopod-like 
form.  The  mandibles  are  vertical,  and  end  in  hollow  points, 
through  which  the  poison  exudes,  the  two  poison-glands 
being  situated  in  the  head.  The  male  spider  is  usually 
much  smaller  than  the  female  ;  the  latter  lay  their  eggs  in 
silken  cocoons.  The  tarantula  (Lycosa)  usually  lives  in 


TRAP-DOOR  SPIDERS. 


363 


holes  in  the  ground,  and  sometimes  conceals  the  opening  by 
covering  it  with  a  few  dead  leaves.  Our  largest  spider  is 
NepMla  plumipes  of  the  Southern  States.  The  common 
garden  spider  is  Epeira  vulgaris  Hentz.  It  lives  about 


Fig.  320. — Development  of  the  Spider. — 'A,  worm-like  stage  ;  .B,  primitive  band  ; 
C,  the  same  more  advanced,  with  rudiments  of  limbs. 

houses  and  in  gardens  ;  its  geometrical  web  is  very  regular. 
The  large  trap-door  spider  (Mygale)  has  four  lung-sacs  in- 
stead of  two,  as  in  the  other  spiders,  and  only  two  pairs  of 
spinnerets.  Mygale  Henzii  Girard 
inhabits  the  Western  plains  and 
Utah  ;  Mygale  avicularia  Linn,  of 
South  America  is  known  to  seize 
small  birds,  and  suck  their  blood. 
There  are  probably  about  six  or 
eight  hundred  species  of  spiders 
in  North  America ;  their  colors 
are  often  brilliant,  and  sometimes, 
from  the  harmony  in  their  colora- 
tion with  that  of  the  flowers  in 
which  they  hide,  or  the  leaves  on 
which  they  may  rest,  elude  the 
grasp  of  insectivorous  birds. 

Sub-class  4.  Hexapoda. — The 
triregional  division  of  the  body  is  better  marked  in  the 
genuine  winged  insects  than  in  the  Myriopods  and  spiders. 
They  have  compound  as  well  as  simple  eyes  ;  two  pairs  of 


Fig.  321.— Embryo  Spider,  still 
more  advanced.  This  and  Fig.  320 
after  Claparede. 


364  ZOOLOGY. 

wings  ;  three  pairs  of  thoracic  legs  ;  often  a  pair  of  jointed 
abdominal  appendages,  besides  the  ovipositor  or  sting  which 
morphologically  represents  three  pairs  of  legs. 

There  are  eight  orders,  forming  two  series  :  first,  the 
Heterometabola,  comprising  -the  Thysanura,  Neuroptera, 
Orthoptera,  Hemiptera,  and  Coleoptera,  in  which  the  meta- 
morphosis is  either  incomplete  or  complete ;  the  body 
shows  a  tendency  to  become  flattened ;  the  prothorax  is 
usually  large  and  flattened  ;  the  mouth-parts  (except  in  the 
Hemiptera)  adapted  for  biting.  There  are  a  number  of 
wingless  forms. 

The  second  series  of  orders,  or  Metabola,  comprising  the 
Diptera,  Lepidoptera,  and  Hymenoptera,  usually  have  a 
cylindrical  body,  with  the  prothorax  small,  the  mouth-parts 
often  adapted  for  sucking  or  lapping  up  liquid  food  ;  with 
a  complete  metamorphosis,  the  larva  being  worm-like, 
cylindrical,  very  unlike  the  adult. 

Order  1.  Thysanura. — The  spring-tails  (Podura)  and 
bristle-tails  (Lepisma)  represent  this  group.  They  are 
wingless,  with  some  affinities  to  the  Myriopods,  and  the 
typical  form  Campodea  (Fig.  324)  is  regarded  as  the  ances- 
tral form  of  the  six-footed  insects,  as  it  is  a 
generalized  type,  and  forms  like  it  may  have 
been  the  earliest  insects  to  appear. 

In  Podura,  the  spring-tail,  and  also  'n 
Smynthurus  (Smynthurus  quadrisignatus 
Pack.,  Fig.  322),  the  characteristic  organ  is 
a  forked  abdominal  appendage  or  "  spring," 
held  in  place  by  a  hook  ;  when  released  the 
spring  darts  backward,  sending  the  insect 

Pig.    V&.-Smyn-    u •    ,    .      ,, 
thurus,  a  spring-tail,    high  in  the  air. 

Our  commonest  Poduran  is  Tomocerus 
plumbeus  Linn.  (Fig.  323),  found  all  over  the  northern 
hemisphere  in  North  America  and  Europe.  The  snow-flea, 
Achorutes  nivicola  Fitch  is  blue-black,  and  is  often  seen 
leaping  about  on  the  snow  in  forests. 

The  Podurans  belong  to  the  suborder  Collembola ;  the 
higher  forms,  which  bear  a  greater  resemblance  to  the  larvae 
of  Neuropterous  insects  and  to  the  young  cockroach,  are 


NEUROPTERA. 


365 


the   Cinura,  to  which  belong  the  genera  Campodea  (Fig. 

324),  Lepisma,  and  Machilis. 

In  these  Thysanura  there  is  no 
spring,  but  the  tail  ends  in  two  or 
three  bristles ;  and  in  Machilis, 
the  highest  form,  there  are  com- 
pound eyes  ;  in  all  there  are 


Fig.  323.— A  Podnrau  (Tomocerm)  and  its  scales.    Much  enlarged. 

jointed  abdominal  appendages,  which 
structures  are  unique  among  Hexa- 
podous  insects.  Campodea  Ameri- 
cana Packard  is  a  small  white  slender 
form,  with  long,  many-jointed  an- 
tennae, and  two  long,  slender  jointed 
caudal  appendages.  It  lives  under 
stones,  and  C.  Cookei  Packard  lives 
in  Mammoth  Cave. 

Order  2.  Neuroptera. — This  group 
of  net-veined  insects  is  interesting 
from  the  fact  that  the  existing 
families  are  widely  separate,  owing 
to  the  geological  extinction  of  inter- 
mediate links  found  fossil  in  the 
Devonian  and  Carboniferous  strata. 
The  mouth-parts  are  free,  adapted 
for  biting  ;  the  wings  are  broad,  the 
hinder  pair  sometimes  larger  than  mandibles ;  a,  maxilla, 
the  front  pair,  and  both  pairs  are  finely  net- veined.  The 


366 


ZOOLOGY. 


metamorphosis  is  either  complete  or  incomplete.  Many  of 
the  species  are  aquatic.  There  are  ten  existing  families, 
and  certain  species  of  most  of  these  families  resemble  or 
anticipate  the  higher  orders  that  succeeded  them  in  time. 
Thus  the  caddis-flies  would  be  easily  mistaken  for  small 
moths ;  the  Mantispa  mimics  Mantis,  the  Psocus  mimics 
the  plant-lice,  and  the  white  ants  which  appeared  in  the 
Coal  Period  foreshadow  the  genuine  ants,  which  first  ap- 
peared in  the  Tertiary  Period,  wonderfully  in  form  as  well 
as  in  the  extreme  differentiation  of  the  individual,  involv- 
ing a  complicated  colony  with  numerous  members  of  the 
entomological  body  politic. 


I 

I 

—  -^ 

I 

i 

i 

I 

V 

I 

i. — Pupa  of  a  Drag- 
(Eschna) 


Fig.  326. — Agrion,  natural  size, 
larval  gill,  much  enlarged. 


and  a,  its 


As  many  of  the  larval  Neuroptera  live  in  the  water,  the 
various  forms  of  external  gills  are  of  high  interest.  In  the 
case-worms,  which  construct  tubes  of  sand,  bits  of  leaves, 
etc.,  the  gills  are  slender  filaments  permeated  by  air-tubes 
and  situated  along  the  side  of  the  body.  In  the  larval  and 
pupal  dragon-fly  (Fig.  325)  the  water  passes  into  the  intes- 
tine, where  there  are  folds  rich  in  minute  tracheal  branches. 
In  the  smaller  dragon -flies,  such  as  Agrion  (Fig.  326),  there 
are  three  long,  leaf-like  gills,  interpenetrated  by  air-tubes. 


WHITE  ANTS. 


367 


In  the  May-fly  (Fig.  327)  the  leaf-like  gills  grow  out  from 
the  sides  of  the  body.  In  the  larval  and  pupal  Perla 
(Fig.  328),  tufts  of  gills  are  situated  on  the  under  side  of 

the  prothorax,  and  in 
the  adult  winged  Pte- 
ronarcys  these  gills 
are  retained.  Both  an 
European  and  Brazil- 
ian Caddis-fly  has  been 
found  to  possess  gills 
in  the  winged  condi- 
tion. 

The  habits  of  the 
Neuroptera  are  most 
interesting ;  the  ant- 
lion  in  the  larval  state 
constructs  a  pitfall  for 
unwary  insects.  Its 
metamorphosis  is  com- 
plete, as  is  that  of  the 
Aphis-lion  (Fig.  329, 
Chrysopa  oculata  Say, 
adult  and  eggs). 

As    an    example    of 

Fig.  887.-May.fly  and  larva,  the  latter  enlarged,     mimicry  among  insects 

is  Mantispa  (Fig.  330), 

which,  in  its  raptorial  fore-legs,  strikingly  resembles  the 
Orthopterous  Mantis  (Fig.  333). 

The  white  ants  top  the  Neuropterous  series  ;  they  live  in 
stumps  and  fallen  trees,  and  in  the  tropics  do  much  harm 
by  undermining  the   sills 
of  houses,  and  destroying 
furniture,  books,  etc.    The 
colonies  are  very  large  and 
populous.     In  our  Termes 
flavipes    there    are    males 
and  females,  workers  and 
soldiers  ;  the  workers  being  small,  ant-like,  with  small  round 
heads,  while  the  soldiers  have  large  square  heads,  with  long 


Fig.  329.—Chi'y80pa  and  group  of  stalked 

eggs. 


368 


ZOOLOGY. 


jaws  ;  the  pupse  are  active.  Fritz  Mfiller  found  in  Brazil 
that  one  species  of  Termes  was  differentiated  into  six 
different  kinds  of  individuals  :  viz.,  a  set  of  winged  and 
wingless  females  ;  winged  and 
wingless  males  ;  workers  and  sol- 
diers. A  male  always  lives  with  a 
female,  and  a  wingless  male  and 
female  may,  on  the  death  of  a 
winged  normal  male  and  female, 
replace  them.  He  found  a  male 
(king)  living  with  thirty-  one  com- 
plemental  females.  In  Cdlotermes 

Fig.  m—Jfantispa  interrupta  there  are  no  workers,  in  Anoploter- 
mes  no  soldiers.     Termes  Mlicosus 
Smeathman,  of  the  west  coast  of 
Africa,  builds  conical  hills  six  feet  or  more  in  height. 

Order  3.  Orthoptera.  —  The  insects  of  this  group,  so  called 
from  the  straight-edged  fore  wings  of  the  grasshoppers, 


Fig.  331.— Freshly-hatched  larva  of 
Mantispa  styriaca.   Enlarged. 


Fig.  332. — Larva  of  the  same,  but 
older,  before  the  first  moult.  En- 
larged.—After  Brauer. 


locusts,  crickets,  etc.,  is  characterized  by  their  net-veined 
wings  and  incomplete  metamorphosis  ;  they  are  connected 
closely  with  the  Neuroptera  by  the  ear- wig  (Forficula). 


SOIWDS  OF  INSECTS. 


369 


Organs  of  hearing  may  be  situated  either  on  the  fore  legs, 
as  in  the  green  grasshoppers,  katydids,  or  at  the  base  of 
the  abdomen,  as  in  the  locusts.  Most  Orthoptera  have  a 
large  ovipositor  by  which  they  burrow  in  the  earth  or  into 
soft  wood,  and  deposit  their  eggs  singly  or  in  masses. 
Mantis  (Fig.  333)  lays  its  eggs  in  a  cocoon-like  mass. 

Many  Orthoptera,  as  the  crickets,  green  grasshoppers, 
katydids,    etc.,  and  locusts,  produce  loud,  shrill  sounds, 


Fjg.  333.— An  African  Mantis,  or  soothsayer,  with  its  egg-mass.— From  Monteiro's 
Angola. 

which  are  sexual  calls.  They  stridulate  in  three  ways — 
i.e.,  first,  by  rubbing  the  base  of  one  wing-cover  on  the 
other  (crickets  and  green  grasshoppers)  ;  second,  by  rub- 
bing the  inner  surface  of  the  hind  legs  against  the  outer 
surface  of  the  front  wings  (some  locusts)  ;  third,  by  rub- 
bing together  the  upper  surface  of  the  front  edge  of  the 
hind  wings  and  the  under  surface  of  the  wing-covers  during 
flight  (some  locusts). 


370 


ZOOLOGY. 


Order  4.  Hemiptera. — Insects  of  this  group  are 
bugs.     They  all   (except  the  bird-lice  and    Thrips} 
sucking  mouth-parts,  the   mandi- 
bles and  first  maxillae  are  bristle- 
*\     /.       like,  and  ensheathed  by  the  labium 
\JL/         or  second  maxillae.     There  are  no 
j^fr    v      palpi   except   in   Thrips    and    the 
X  vBBv  >    bird-lice.     The  metamorphoses  are 
f  •  I  J       incomplete,  the  larva  being  like  the 
\  (       adult,  except  that  the  wings  are  ab- 

sent. Many  bugs  secrete  a  disa- 
t£&iK'iiSS^  greeable  fluid  from  glands  seated  in 
bus-  the  metathorax.  -  The  lice  are  low, 

wingless  parasitic  Hemiptera.    The 
squash-bug  (Fig.  334,  Coreus  tristis)  and  chinch-bug 
sus  leucopterus  Uhler)  are  types  of  the  order. 


called 
have 


Fig.  336.— Seventeen -year  Locust,    a,  b,  pupa  ;  d,  incisions  for  eggs.— After  Biley. 

An  aberrant  form  is  Thrips  (Fig.  335,  Thrips  cereaUum), 

with  long,  slender  white  wings  and  free  biting  mouth-parts. 

While  most  insects  live  but  a  year  or  two,  or  three  at  the 


PLANT  LICE. 


371 


most,  the  seven  teen -year  locust  (Cicada  septemdecim  Linn., 
Fig.  336)  lives  over  sixteen  years  as  a  larva,  finishing  its 
transformations  on  the  seventeenth  ;  there  is  also,  accord- 
ing to  Riley,  a  thirteen-year  variety  of  this  species. 


Fig. 3S7.— Spittle  insect 
its  natural  size. 


Fig.  338.— Cochineal  insect, 
male  ;  female  natural  size  and 
enlarged. 


The  froth  insect  (Ptyelus  lineatus,  Fig.  337)  abounds  on 
grass  in  early  summer.  The  cochineal  insect  ( Coccus  cacti) 
belongs  to  the  Coccidm,  or  bark-lice ;  the  dried  female  is 
used  as  a  dyestuff,  and  abounds  in  Central  America. 

The  plant-louse  (Fig.  339,  Aphis  mail  Fabr.)  is  provided 
with  two  tubes  on  the  hind-body  from  which  honey-dew 


Fig.  339.— Apple  Aphis.    Natural  size  and  enlarged. 

drops,  which  attracts  ants,  wasps,  etc.  In  summer  the 
plant-lice  reproduce  asexually,  and  as  there  may  be  nine  or 
ten  generations,  one  virgin  aphis  may  become  the  parent  of 
millions  of  children  and  grand-children. 


372 


ZOOLOGY. 


Order  5.  Coleoptera. — The  beetles  form  a  homogeneous 
and  easily  circumscribed  group,  all  having  the  fore-wings 
thickened,  not  used  in  flight,  and  forming  sheaths  (elytra 


'6  a 

Fig.  310.— Pine  weevil.    «,  larva  ;  ft,  pupa. 

or  wing-covers)  for  the  hinder  pair.  The  mouth-parts  are 
free  and  adapted  for  biting.  The  metamorphosis  is  com- 
plete. The  young  or  larvae  of  beetles  are  called  grubs. 
Examples  of  beetles  and  their  transformations  are  the  pine 


Pig.  341.— June  Beetle  and  its  transformations,    1,  pupa;  2,  larva.— After  Kiley. 

weevil  (Fig.  340,  Pissodes  stroU  Peck.)  and  the  June  beetle 
(Fig.  341,  Lachnosterna  fusca  Frohl.).  The  oil  beetle  is 
remarkable  for  passing  through  three  larval  stages  (Fig. 


OIL  BEETLE. 


373 


,  Meloe  angusticollis  Say),  the  first  larva  being  minute 
and  parasitic  on  bees,  sucking  their  blood,  while  in  the 


Fig.  342. — Oil  Beetle.   a,  first  larva ;  &,  second  larva ;  c,  third  larva  ;  d,  pupa. 

second  and  third  stages  it  feeds  on  the  pollen  mass  designed 
for  the  young  bees. 


Fig.  343,—Stylops  childreni,  male,  dorsal  and  side  view.    Much  enlarged. 

The  blister  beetles  (Lytta  marginata)  undergo  a  similar 
series    of   transformations    called    a  hypermetamorphosis. 


374 


ZOOLOGY. 


The  most  aberrant  of  beetles  is  Stylops  (Figs.  343  and  344, 
8.  childreni  Westwood),  the  male  of  which  has  minute  fore 


Fig.  344.—  Stylops  childreni.  female. 

0,  parasitic  in  the  abdomen  of  a  bee  ; 

1,  top  view  of  the  same.     Much  en- 
larged. 


Fig.  345.—  Astraptor  illuminator,  larva. 


Fig.  346.— The  early  stages  of  the  common  House-fly.  A,  dorsal  and  side  view  of 
the  larva ;  a,  air-tubes  :  sp,  epiraclo.  C,  the  spiracle  enlarged.  F,  head  of  the  same 
larva,  enlarged  ;  U,  labrum  (?);  md,  mandibles  ;  mx.  maxillae  ;  at,  antennae.  E,  a 
terminal  spiracle  much  enlarged.  D,  puparium  :  sp.  epiracle.  All  the  figures  much 
enlarged. 

wings.     The  female  is  wingless,  grub-like,  imperfectly  de- 
veloped, and  is  viviparous,  the  young  issuing  from  her  body 


THE  JIG  USE-FLY. 


375 


in  all  directions.  A  few  beetles  are  phosphorescent.  Such 
are  the  fire-flies,  the  cucuyo  of  the  West  Indies,  the  glow- 
worm, and  certain  grubs,  such  as  Astraptor  illuminator 
(Fig.  345),  Melanactes,  and  the  young  of  a  snapping  beetle. 


Fig.  347.— Bot-fly  of  the  ox  and  its  larva. 

We  now  come  to  the  second  series  of  orders,  the  Meta- 
lola. 

Order  6.  Diptera. — The  common  house-fly  (Fig.  346)  is 
a  type  of  this  division,  all  the  members  of  which  haye  but 
two  wings,  while  the  tongue  is  especially  developed  for  lap- 
ping up  liquids.     The  common  house^ 
fly  lives  one  day  in  the  egg  state,  from 
five  days  to  a  week  as  a  maggot,  and 
from  five  to  seven  days  in  the  pupa 
state.     It  breeds  about  stables. 

The  Tachina-fly  is  beneficial  to  man, 
from  its  parasitism  in  the  bodies  of 
caterpillars  and  other  injurious  insects. 

The  bot-fly  (Fig.  347,  Hypoderma 
lovis  DeGeer)  is  closely  allied  to  the 
house-fly,   but  the   maggot    is  much 
larger.    The  larval  bot-fly  of  the  horse  lives  in  the  stomach, 
that  of  the  sheep  in  the  frontal  sinus. 

The  Syrphus  flies  (Fig. '348,  Syrphus  politus  Say)  mimic 
wasps  ;  they  are  most  useful  in  devouring  aphides. 


376 


ZOOLOGY. 


Fig.  .349. — Metamorphosis  of  SarcottsyUa penelrans,  or  jigger,  which  lives  in  the  toe 
of  the  natives  of  tropical  America.  1,  egg  ;  2,  embryo ;  3,  larva  ;  4,  cocoon ;  5,  pupa : 
6,  fecundated  female  ;  7,  the  same  on  the  third  day  from  its  entrance  under  the  skin 
of  ifg  human  host ;  8,  the  same  after  several  days'  residence  in  the  skin  of  its  host ; 
9,  fully  grown  female  magnified  four  times  ;  10,  head  of  the  same  still  more  enlarged  ; 
11,  the  female  before  it  has  entered  the  skin  of  its  host  ;  12,  the  mouth-parts,  much 
enlarged  :  m,  mandible?  ;  d,  maxillary  palpi ;  w,  under-lip  or  labium.— After  Karsteu 
and  Guy  on. 


THE  HESSIAN-FLY. 


377 


Fig.  350.— Hessian-fly,    a,   larva  ;  b,   pu] 
,  -.          c,  incision    in  wheat  stalk    for  larva.— Af 

are  large  flies,   Fitch. 


The  fleas  (349)  are 
wingless  flies,  allied  to 
winged  forms  intermedi- 
ate between  the  house- 
flies  and  crane-flies. 

In  the  two-winged  gall- 
flies (Fig.  350,  Cecidomyia 
destructor  Say,  or  H  e  s  - 
sian-fly)  the  body  is  small 
and  slender,  with  long 
antennae.  The  crane-flies 
(Tipula) 
standing  near  the  head  of 
the  order,  and,  like  the 
flea  and  gall-fly,  the 
chrysalis  is  enclosed  in  a 
cocoon,  there  being  no 
puparium  or  pupa-case, 
as  in  the  lower  flies. 
Lastly,  we  hav.e  the  mus- 
quito  (Figs.  351  and  352), 
whose  larva  is  aquatic, 
and  breathes  by  a  process 
on  the  end  of  the  body, 
containing  a  trachea. 

Order1^.  Lepidoptera. — 
The  butterflies  and  moths 
form  a  well-defined  group, 
and  are  known  by  their 
scaly  bodies  (Fig.  353), 
the  spiral  maxillae  or 
tongue,  rolled  up  between 
the  two  large  labial  palpi, 
and  their  usually  broad 
wings.  As  the  butterfly, 
the  type  of  the  order,  has 
been  described  at  some 
length,  we  will  only 
enumerate  some  of  the 


larva ;  c,  its  respiratory  tube. 
ji,  yu^o, ,  d,  respiratory  tube,  a,  two  paddles 
at  the  end  of  the  body. 


Fi"1.  352.— Head  of  Mosquilo  enlarged,  a, 
antenme  ;  m.  mandibles  ;  ma-,  maxilla  ;  mp, 
maxillary  palpi;  Ig,  labium. 


378 


ZOOLOGY. 


typical   forms.      The   lowest   group   are   the   plume-moths 
(Pterophorus),  in  which  the   wings  are  fissured.     Above 


Fig.  353. — Showing  mode  of  ar- 
rangement of  the  scales  on  the  wings 
of  a  Moth. 


Fig.  354.— Angoumois,  Grain  Moth. 


Fig.  355.— Grain  Moth,  Tinea  granella.    a,  larva  ;  5,  pupa,  nat.  size  and  enlarged  ; 
c,  grain  of  wheat  held  together  by  a  web.— After  Curtis. 


Fig.  356.— Army-worm  Moth.  a.  male  ;  ft,  female;  c,  eye;  d,  male  ;   e,  portion  of 
female  antenna.    Much  magnified.— After  Riley. 

them  stand  the  clothes  and  grain  moths  (Figs.  354  and  355), 
which  are  minute  moths  with  narrow  wings. 


THE  COTTON-WORM. 


379 


ing. 

of  Aletia 
worm. 


j,  caterpillar,  and  moth 
the  Cotton  Army- 


The  larger  moths  are  represented  by  the  canker-worm, 
the  grass  army-worm  (Fig.  356),  and  the  cotton  army-worm 

(Fig.  357),  so  destructive  to 
vegetation  ;  the  silk  -  worm 
moth  (Bombyx  mori  Linn.), 
of  the  Old  World,  and  the 
American  silk-worm  ( Telea 
Polyphemus  Linn.).  Certain 
species  of  the  silk  -  worm 
family,  called  basket-worms 
((Eceticus),  live  in  cases  con- 
structed of  short  or  long  strips 
(Fig.  358).  Our  native  species 
is  Thyridopteryx  ephemercefor- 
mis  Haworth. 

The  hawk-moths  (Sphinx)  are  distinguished  by  their 
large  size  and  very  long  tongue.  The  butterflies  differ  from 
the  moths  in  having  knobbed  anten- 
nae, while  the  chrysalides  are  often 
ornamented  with  golden  or  silvery 
spots. 

Order  8.  Hymenoptera. — The  bees 
stand  at  the  head  of  the  insect  series 
in  perfection  and  specialization  of 
parts,  especially  the  organs  of  the 
mouth,  and  from  the  fact  that  in  the 
course  of  the  metamorphosis  from 
the  larva  to  the  pupa  the  first  ab- 
dominal segments  become  transferred 
to  the  thorax — a  striking  instance  of 
the  principle  of  transfer  of  parts 
headward.  In  the  large  head,  spheri- 
cal thorax,  and  short,  conical  abdo- 
men, the  bees  are  opposed  to  the 
dragon-flies  and  other  Neuroptera, 
in  which  the  abdomen  is  long,  the  Ba^et-worm£a8Nat°uraf  Sb" 
thorax  composed  of  three  homogene- 
ous segments,  and  the  mouth-parts  only  adapted  for  biting. 
In  the  bee  there  is  a  marked  differentiation  of  the  parts  of 


380  ZOOLOGY. 

the  first  and  second  maxillae  ;  the  tongue  or  fleshy  prolonga- 
tion of  the  second  maxillae  (labium,  see  Fig.  359,  g)  being 
very  long  and  adapted  for  lapping  up  liquid  food  in  the 
bottom  of  flowers. 

The  Hymenoptera  are  represented  by  the  saw-flies,  the 
gall-flies,  the  ichneumon-flies  and  the  ants,  the  sand-wasps, 
mud-wasps  (Fig.  368),  paper-making  wasps,  and  bees. 

The  lowest  family  is  the  Uroceridce,  or  horn-tails  (Fig. 
360,  larva  of  Tremex  columla  Linn.),  whose  fleshy  white 


Fig.  359.— Side  view  of  the  front  part  of  the  head  of  the  Humble  Bee.  a,  clypeus 
covered  with  hairs  :  b,  labrum  ;  c,  the  fleshy  epipharynx  partially  concealed  by  the 
base  of  the  mandibles  (c?);  e,  lacinia  or  blade  of  the  maxillae,  with  their  two-jointed 
palpi  (/)  at  the  base  ; .;,  the  labium  to  which  is  appended  the  ligula  (ig)  ;  below  are 
the  labial  palpi ;  A,  the  two  basal  joints  ;  k,  compound  eyes. 

larvae  bore  in^trees.  The  adults  are  large,  with  a  long,  saw- 
like  ovipositor.  In  the  saw-flies  (Tenthredinidce,  Fig.  361, 
the  pear-slug,  Selandria  cerasi  Peck)  the  larva  strongly  re- 
sembles a  caterpillar,  having  eight  pairs  of  abdominal  feet. 
The  gall-flies  (Fig.  362,  Cynips)  are  small  Hymenoptera 
which  lay  eggs  in  the  leaves  or  stems  of  the  oak,  etc.,  which, 
from  the  irritation  set  up  by  their  presence,  causes  the  de- 
formation termed  a  gall. 


HABITS  OF  ANTS. 


381 


The  ichneumon-flies  (Fig.  363)  are  very  numerous  in  spe- 
cies and  individuals  ;  by  their  ovipositor,  often  very  long, 
they  pierce  the  bodies  of  caterpillars,  inserting  several  or 
many  eggs  into  them  ;  the  larvas  develop  feeding  only  on 
the  fatty  tissues  of  their  host,  but  this  usually  causes  the 
death  of  the  caterpillar  before  its  transformation.  Certain 
minute  species,  with  veinless  wings  (Fig.  364,  Platyg aster), 
of  the  canker-worm  eggs,  are  egg-parasites,  ovipositing  in 
the  eggs  of  butterflies,  dragon-flies,  etc. 


Fig.  360.— Horn- 
tail  :  larva  of  Tre- 
mexcolumba.  Nat. 
size. 


Fig.  362.— Gall-fly  of  oak. 


Fig.  3(53.— An  Ichneuinou-fly. 


Fig.  361.— Pear  Slug, 
natural  size,  gnawing 
leaves,  a,  larva  en- 
larged ;  6,  the  fly. 


parasite  of  Canker- 


The  family  of  ants  is  remarkable  for  the  differentiation 
of  the  species  and  the  consequent  complexity  of  the  colony, 
the  division  of  labor  and  the  reasoning  powers  manifested 
by  the  workers  and  soldiers,  which,  with  the  males  and 
females,  constitute  the  ant-colony. 

Certain  ants  enslave  other  species  ;  have  herds  of  cattle, 
the  aphides ;  build  complicated  nests  or  formicaries  (Fig. 
860),  tunnel  broad  rivers,  lay  up  seeds  for  use  in  the  winter- 


ZOOLOGY. 


time,  are  patterns  of  industry,  and  exhibit  a  readiness  in 
overcoming  extraordinary  emergencies,  which  show  that 


Fig.  365.— (Ecodoma,  or  Leaf-cutter  Ant  of  Nicaragua.— After  Belt. 

they  have  sufficient  reasoning  powers  to  meet  the  exigencies 
of  their  life  ;  their  ordinary  acts  being  instinctive — namely, 


Fig.  366.— Diagram  of  an  ant's  nest  (CEcodoma),  the  chambers  below  containing 
the  ant  food.— After  Belt. 

the  results  of  inherited  habits.      The  leaf-cutter  ants  of 
Central   and   South  America  (Fig.  365)  are  famous  from 


MUD-  WASPS.  383 

their  leaf -cutting  habits  ;  the  soldiers  have  large  triangular 
heads,  while  the  workers  have  much  smaller  rounded  heads. 
Fig.  367  represents  a  species  of  Eciton. 


Fig.  367.—  Ecitou.  Fig.  368.— Mud-dauber. 

The  mud-daubers  (Pelopc&us,  Fig.  368)  build  their  nests 
against  stone  walls,  of  pellets  of  mud,  while  the  sand-  and 
mud-wasps  dig  deep  holes  (Fig.  369,  Sphex  ichneumonea 


Fig.  369.— Sand- wa«p  (Sphex).    Natural  size. 

Linn.)  in  gravelly  walks,  and  have  the  instinct  to  sting 
grasshoppers  in  one  of  the  thoracic  ganglia,  thus  paralyzing 
the  victim,  in  which  the  wasp  lays  her  eggs  ;  the  young 


384 


ZOOLOGY. 


hatching,  feed  upon  the  living  but  paralyzed  grasshoppers, 
the  store  of  living  food  not  being  exhausted  until  the  larval 

wasp  is  ready  to  stop  eating 
and  finish  its  transformations. 
The  genuine  paper-making 
wasps  are  numerous  in  species; 
here  the  workers  are  winged, 
and  only  differ  from  the 
females  or  queens  in  being 
rather  smaller  and  with  unde- 
veloped ovaries.  The  series  of 
genera  from  Odynerus,  which 
builds  cells  of  mud,  and  in 
which  there  are  no  workers, 
up  to  those  which  have  work- 
a  ers  and  build  paper  cells,  such 
as  PoUsteSf  is  quite  continu- 
ous. The  genuine  paper- 
making  wasps,  such  as  Vespa, 
build  several  tiers  of  cells,  ar- 
c  ranged  mouth  downward,  and 
enveloped  by  a  wall  of  several 
thicknesses  of  paper.  In  the 
Vespcv,  the  females  found  the 
colony,  and  raise  a  brood  of 
workers,  which  early  in  the 
e  summer  assist  the  queen  in 
completing  the  nest. 

The  bees  also  present  a 
gradual  series  from  those 
which  are  solitary,  living  in 
holes  in  the  earth,  like  the 
ants  (Fig.  370,  nest  of  An- 
drena  vicina  Smith),  and  form- 

^^£j&^td$^  ing  silk-lined  earthen  cocoons, 
Eme9rtornSSf  dei)osited  b?  the  ™e-~  to  those  which  are  social,  with 

winged  workers,  slightly  dif- 
fering from  the  queens.  The  queen  humble-bee  hybernates, 
and  in  the  spring  founds  her  colony  by  laying  up  pellets  of 


Fig.  370.— Nest  of  Andrena.    g, 
of   ground;     a,    first-made  cell, 


level 


CLASSIFICATION  OF  INSECTS.  385 

pollen  in  some  subterranean  mouse-nest  or  in  a  stump,  and 
the  young  hatching,  gradually  eat  the  pollen,  and  when  it 
is  exhausted  and  they  are  fully  fed,  they  spin  an  oval  cylin- 
drical cocoon ;  the  first  brood  are  workers,  the  second  males 
and  females.  The  partly  hexagonal  cells  of  the  stingless 
bees  of  the  tropics  (Melipona)  are  built  by  the  bees,  while 
the  hexagonal  cells  of  the  honey-bee  are  made  by  the  bees 
from  wax  secreted  by  minute  subcutaneous  glands  in  the 
abdomen.  Though  the  cells  are  hexagonal,  they  are  not 
built  with  mathematical  exactitude,  the  sides  not  always 
being  of  the  same  length  and  thickness. 

The  cells  made  for  the  young  or  larval  drones  are  larger 
than  those  of  the  workers,  and  the  single  queen  cell  is  large 
and  irregularly  slipper-shaped.  Drone  eggs  are  supposed  by 
Dzierzon  and  Siebold  not  to  be  fertilized,  and  that  the  queen 
bee  is  the  only  animal  which  can  produce  either  sex  at  will. 
Certain  worker-eggs  have  been  known  to  transform  into 
queen  bees.  On  the  other  hand,  worker-bees  may  lay 
drone  eggs.  The  maximum  longevity  of  a  worker  is  eight 
months,  while  some  queens  have  been  known  to  live  five 
years.  The  latter  will  often,  under  favorable  circum- 
stances, lay  from  2000  to  3000  eggs  a  day.  The  first  brood 
of  workers  live  about  six  weeks  in  summer,  and  are  suc- 
ceeded by  a  second  brood. 


CLASS  II.— INSECTA. 

A  distinct  head,  thorax,  and  abdomen  ;  breathing  by  tracheae, ;  uwudly 
with  a  metamorphosis. 

SUB-CLASS  I.  Malacopoda. — Numerous  simple  spiracular  openings  with 
isolated  tracheal  twigs  ;  nervous  system  with  an  incomplete 
chain  of  minute  ganglia,  but  the  cords  widely  separated 
(Periputus). 

SUB-CLASS  II.  Myriopoda.— Thorax  and  abdomen  forming  a  continuous 
region,  with  from  six  to  two  hundred  joints,  each  bearing  u 
pair  of  genuine  legs. 

Order  1.    Chilognatha.—Body  cylindrical  or  flattened,   with  no 
sternum  ;  a  distinct  metamorphosis  (Julus,  Polydesmus). 


386  ZOOLOGY. 

Order  2.  Pauropoda.— Microscopic  ;  body  of  six  to  nine  segments 
besides  the  head  (Pauropus). 

Order  3.  Chilopoda.— Sternum  large,  body  flattened  (Scolopendra, 
Lithobius). 

SUB-CLASS  III.  Arachnida. — Head  and  thorax  intimately  united  ;  no 
antennae,  and  only  one  pair  of  maxillae  ;  no  genuine  abdo- 
minal legs. 

Order  1.  Acarina. — No  thorax  separate  from  the  abdomen  (Acarus, 
Ixodes). 

Order  2.  Pedipalpi. — Maxillary  palpi  often  ending  in  a  forceps  or 
claw ;  abdomen  distinctly  segmented  (Scorpio,  Chelifer, 
Phalangium). 

Order  3.  Araneina. — Abdomen  rounded,  bearing  two  or  three 
pairs  of  spinnerets,  and  attached  by  a  slender  pedicel  to  the 
thorax  ;  no  metamorphosis  (Epeira,  Mygale). 

SUB-CLASS  IV.  Hexapoda. — Antennas  always  present,  and  two  pairs  of 
maxillae  ;  six  thoracic  legs  ;  a  genuine  metamorphosis. 

Order  1.  Thysanura. — Wingless,  minute,  with  a  spring,  or  ab- 
domen ending  in  a  pair  of  caudal  stylets ;  usually  no 
compound  eyes ;  no  metamorphosis  (Podura,  Campodea, 
Lepisma). 

Order  2.  Neuroptera.— Winged,  net-veined,  of  equal  size,  pupa 
often  active  ;  abdomen  often  long  and  slender  (Ephemera, 
Libellula,  Phryganea,  Chrysopa,  Perla,  Termes). 

Order  3.  Orthoptera.  —  Wings  net-veined  ;  fore- wings  narrow, 
straight,  not  often  used  in  flight ;  metamorphosis  incomplete1; 
pupa  active  (Forlicula,  Locusta,  Caloptenus,  Phaneroptera, 
Acheta). 

Order  4.  Hemiptera. — Mouth-parts  forming  a  sucking  beak  ;  pro- 
thorax  usually  large ;  fore-wings  often  thickened  at  base  ; 
pupa  active  (Coreus,  Anna,  Pentatoma,  Cicada,  Coccus, 
Aphis). 

Order  5.  Coleoptera.  —  Fore-wings  thick,  ensheathing  the  hinder 
pair,  which  are  alone  used  in  flight ;  mouth-parts  free, 
adapted  for  biting  ;  metamorphosis  complete  (Doryphora, 
Clytus,  Lucanus,  Harpalus,  Cicindela), 

Order  6.  Diptera.  —  Only  two  wings  ;  mouth-parts  adapted  for 
lapping  and .  sucking  ;  a  complete  metamorphosis  (Musca, 
(Estrus,  Syrphus,  Cecidomyia,  Tipula,  Culex). 


CLASSIFICATION  OF  INSECTS. 


387 


Order  7.  Lepidoptera.  —  Body  and  wings  covered  with  scales  ; 
maxillae  lengthened  into  a  very  long  tongue  ;  larvae 
(caterpillars)  with  abdominal  legs  (Tinea,  Geometjra,  Noctua, 
Bombyx,  Sphinx,  Papilio). 

Order  8.  Hymenoptera.  —  Wiugs  clear,  with  few  veins  ;  mouth- 
parts  with  a  variety  of  functions,  i.e.,  biting,  lapping 
liquids,  etc.  In  the  higher  families  the  thorax  consists  of 
four  segments,  the  first  abdominal  segment  of  the  larva 
being  transferred  to  the  thorax  in  the  pupa  and  imago. 
Metamorphosis  complete.  (Tenthredo,  Cynips,  Ichneumon, 
Sphex,  Vespa,  Apis.) 


TABULAR  VIEW  OF  THE  SUB-CLASSES  AND  ORDERS  OF  INSECTA. 


i  * 


• 

^^  ^ 


I 

C*  cd 


HEXAPODA 


^     'S     i 


ARACHNIDA.          MYRIOPODA. 


INSECTA. 

Laboratory  Work. — In  dissecting  My  riopods,  spiders  and  insects,  the 
dorsal  portion  of  the  integument  should  be  carefully  removed  with 
fine  scissors,  leaving  the  hypodermis  untouched  ;  this  should  then  be 
raised,  disclosing  the  delicate  heart  or  dorsal  vessel.  The  alimentary 
canal  will  be  found  passing  through  the  middle  of  the  body  ;  it  should 
be  laid  open  with  the  scissors,  or  better,  a  hardened  alcoholic  specimen 
can  readily  be  cut  in  two  longitudinally,  and  if  the  section  is  true,  the 
resophagus  and  crop — for  example,  of  a  locust — can  be  laid  open,  and 


388 


ZOOLOGY. 


the  rows  of  teeth  examined.  The  thoracic  and  abdominal  portions  of 
the  nervous  system,  which  lies  loosely  on  the  floor  of  the  body,  can  be 
readily  found  by  raising  the  alimentary  canal ;  but  the  brain  and  infra- 
oesophageal  ganglia  can  best  be  detected  by  a  longitudinal  section  of 
the  head.  The  ovaries  always  lie  above  the  intestine,  and  the  two 
oviducts  unite  below  the  nervous  cord  to  form  the  common  duct  which 
opens  on  the  ventral  side  of  the  third  segment  in  front  of  the  anus, 
which  is  situated  dorsally.  Insects  should  be  dissected  in  a  shallow 
pan  lined  with  wax  or  cork,  and  the  parts  floated  out ;  fresh  specimens 
are  desirable.  The  body  may  also  be  dissected,  each  segment  with  its 
appendages  being  separated  and  glued  in  their  true  sequence  to  a  card. 
By  simply  dissecting  an  insect  in  this  way,  the  student  will  acquire  a 
valuable  knowledge  of  the  external  structure  of  insects. 


Dragon-fly  (Diplax  Elisa). 


CHAPTER  VIII. 


BRANCH  VIIL— VERTEBRATA. 

General  Characters  of  Vertebrates. —  The  fundamental 
characters  of  the  Vertebrates  are  not  the  possession  of  a 
segmented  vertebral  column,  enclosing  a  nervous  cord  and  a 
skull,  and  containing  a  genuine  brain,  for  these  features, 
though  common  to  most  Vertebrates,  are  wanting  in  the 
lancelet  (Amphioxus)  and  in  a  degree  in  the  hag-fish,  and 
even  the  lamprey ;  but  the  essential  character  is  the  division 
of  the  body-cavity  by  the  notochord  (in  the  lancelet,  etc.), 
or  by  the  back-bone  of  higher  Vertebrates  into  two  sub- 
ordinate cavities,  the  upper  (neural)  containing  the  nervous 
cord,  and  the  lower  (enteric)  the  digestive  canal  and  its  ap- 
pendages and  the  heart.  JThese  are  the  only  characters  which 
will  apply  to  every  known  Vertebrate  animal  (compare  p.  226 
with  Figs.  371,  375  and  376.) 

In  general,  however,  the  Vertebrates  are  distinguished 
from  the  members  of  the  other  branches  by  the  following 
characters  :  they  are  bilaterally  symmetrical  animals,  with  a 
dorsal  and  ventral  surface,  a  head  connected  by  a  neck  with 
the  trunk ;  with  two  eyes  and  two  ears,  and  two  nasal  open- 
ings, always  occupying  the  same  relative  position  in  the  head  ; 
an  internal  cartilaginous  or  bony,  segmented  skeleton,  con- 
sisting of  vertebrae,  from  the  bodies  of  which  are  sent  off 
dorsal  processes  which  unite  to  form  a  cavity  for  a  spinal 
cord,  the  latter  sending  off  spinal  nerves  in  pairs  *  correspond- 
ing to  the  segmentations  (vertebrae)  of  the  spinal  column. 

*  Except  in  Amphioxus,  in  which  the  spinal  nerves  arise  right  and 

left  alternately. 


390 


ZOOLOGY. 


From  the  underside  of  the  vertebrae  are  sent  off  processes 
articulating  with  the  ribs,  which  enclose  the  digestive  and 
central  circulatory  organs.  There  is  a  skull  formed  by  a  con- 
tinuation of  the  vertebral  column,  enclosing  a  genuine  brain, 
consisting  of  several  pairs  of  ganglia.  To  the  vertebral  col- 
umn are  appended  two  pairs  of  limbs,  supported  by  rays  ir- 
regularly repeated,  or  a  series  of  bones  of  a  definite  number, 


Fig.  3~1.— Transverse  section  of  a  worm,  of  Amphioxus,  and  of  a  Vertebrate  con- 
trasted, a,  outer  or  skin  layer ;  b,  dermal  connective  layer ;  c,  muscles ;  d,  seg- 
mental  organ  :  A,  arterial,  and  i,  venous  blood-vessel ;  g.  intestine  ;  I,  notochord.— 
After  Haeckel. 

attached  to  the  vertebral  column  by  a  series  of  bones  called 
respectively  the  shoulder  and  pelvic  girdle. 

It  will  be  observed  that  the  fact  of  segmentation,  so  prom- 
inent a  feature  in  the  Worms  and  Arthropods,  survives,  or  at 
least  reappears  in  a  marked  degree  in  the  Vertebrates,  as 
seen  not  only  in  the  vertebral  column,  but  in  the  arrangement 
of  the  spinal  nerves.  It  is  perceived  also  in  the  arrangement 
of  the  muscles  into  masses  corresponding  to  the  vertebrae ; 
and  in  the  segmental  organs  or  tubes  forming  the  kidneys  of 
the  sharks  and  rays,  while  segmentation  is  especially  marked 
in  the  disposition  of  the  primitive  vertebrae  of  the  early  em- 
bryos of  all  Vertebrates. 

The  digestive  canal  consists  of  a  mouth  with  lips  or  jaws, 
armed  with  teeth,  a  pharynx  leading  to  the  lungs  ;  an  oesoph- 
agus and  thyroid  gland  ;  sometimes  a  crop  (ingluvies),  often 
a  fore-stomach  (proventriculus)  ;  a  stomach  and  intestine, 
cloaca  and  vent.  Into  the  beginning  of  the  intestine  passes 
a  duct  leading  from  a  large  liver ;  a  gall-bladder,  usually  a 
pancreas,  and  a  spleen,  also  communicating  with  the  intestine. 
The  products  of  digestion  do  not  all  pass  through  the  walls 
of  the  stomach  and  directly  enter  the  circulation,  as  in  the 
invertebrates,  but  there  is  a  system  of  intermediate  vessels 


NERVOUS  SYSTEM  OF  VERTEBRATES.  391 

called  the  lacteal  system  or  absorbents,  which  take  up  a  part 
of  the  chyle  from  the  digestive  organs  and  convey  it  to  the 
blood-vessels. 

There  is  a  true  heart,  with  one,  generally  two,  auricles,  and 
one  or  two  ventricles  with  thick,  muscular  walls,  and  besides 
arteries  and  veins,  a  capillary  system,  i.  e.,  minute  vessels 
connecting  the  ends  of  the  smaller  arteries  with  the  smaller 
veins.  There  are  no  genuine  capillaries  in  the  lower  animals 
exactly  comparable  with  those  of  the  Vertebrates. 

The  blood  is  red  in  all  the  Vertebrates  except  the  lancelet, 
and  contains  two  sorts  of  corpuscles,  the  white  corpuscles 
like  the  blood-corpuscles  of  invertebrates,  and  red  corpuscles 
not  found  in  invertebrates,  and  which  are  said  by  some 
authors  to  be  derived  from  the  white  corpuscles. 

While  fishes  and  larval  Amphibians  breathe  by  gills,  all  land 
and  amphibious  Vertebrates  breathe  the  air  directly  by  means 
of  cellular  sacs  called  lungs,  and  connected  by  a  trachea  with 
the  pharynx.,  the  trachea  being  situated  beneath  the  oesopha- 
gus, and  the  opening  from  the  mouth  into  the  pharynx  lead- 
ing into  the  trachea  being  placed  below  the  throat  or  passage 
to  the  oesophagus.  The  air  filling  the  cells  or  cavities  of  the 
lungs  passes  by  osmose  through  the  walls  of  the  cells  into  the 
blood  sent  by  the  heart  through  the  pulmonary  artery,  and 
after  being  oxygenated  it  returns  by  the  pulmonary  vein  to 
the  heart.  On  the  other  hand,  carbonic  acid  passes  from 
the  blood  oub  of  the  lungs  through  the  trachea. 

The  nervous  system  of  Vertebrates  consists  of  a  brain  and  '. 
spinal  cord.  The  brain  consists  of  four  pairs  of  lobes,  i.  e., 
the  olfactory  lobes,  cerebral  hemispheres,  the  optic  thalami 
(Thalamencephalon)  and  pineal  gland,  and  the  optic  lobes;  and 
two  single  divisions  :  the  cerebellum  and  the  beginning  of  the 
spinal  cord,  called  the  medulla  oUongata.  The  olfactory  lobes 
are  the  most  anterior,  and  send  off  the  nerves  of  smell  to  the 
nose.  The  cerebral  hemispheres  in  the  fishes  and  amphibians 
are  little  larger  than  the  adjoining  lobes,  but  in  the  reptiles, 
become  larger,  until  in  the  mammals,  and  especially  in  the 
apes  and  man,  they  fill  the  greater  part  of  the  brain-box  and 
overlap  the  cerebellum  ;  the  latter,  in  the  mammals,  also 
exceeding  all  the  other  lobes  in  size,  excepting  the  cerebrum. 


392 


ZOOLOGY. 


Attached  to  a  downward  prolongation  (infundibulum)  of  the 
optic  thalami  is  the  curious  pituitary  body.  The  medulla 
sends  nerves  to  the  skin  and  muscles,  giving  sensibility  and 
motion  to  the  face,  eyes  and  nose,  to  the  larynx  and  sensitive 
portion  of  the  lungs ;  a  pair  also  is  sent  to  the  lungs  and 
heart.  If  the  spinal  marrow  is  severed,  the  parts  below  are 
paralyzed  ;  if  the  medulla  is  cut  or  broken  up  mammals  die 
at  once,  while  the  lower  Vertebrata  die  sooner  or  later. 
The  brain  in  an  embryo  originally  consists  of  three  vesi- 
cles or  primitive  lobes  ;  and  the  correspondence  between 


Fig.  372.— Diagrammatic,  longitudinal  and  vertical  section  of  a  Vertebrate  brain. 
Mb,  mid  brain ;  what  lies  in  front  of  this  is  the  fore  brain,  and  what  lies  behind,  the 
hind  brain.  L,  lamina  terminalis  ;  Olf,  olfactory  lobes  ;  Hmp,  cerebral  hemi- 
spheres ;  Th  E,  thalamencephalon  ;  Pn,  pineal  gland  ;  Py,  pituitary  body  ;  FM,  fo- 
ramen of  Munro  ;  CS,  corpus  striatum  ;  7%,  optic  thalamus;  CO,  corpora  quadri- 
gemina  ;  CO,  crura  cerebri;  Cb,  cerebellum  ;  PV,  pons  varolii ;  MO,  medulla  oblon- 
gata ;  /,  olfactorii ;  //,  optici ;  ///,  point  of  exit  from  the  brain  of  the  Motores 
oculorum  ;  IV,  of  the  pathetic! ;  F/,  of  the  abducentes  ;  V-XI1,  origin  of  the  other 
cerebral  nerves  ;  1,  olfactory  ventricle ;  2,  lateral  ventricle  ;  3,  third  ventricle ;  4, 
fourth  ventricle.— After  Huxley. 

the  three  primitive  lobes,  called  respectively  the  fore,  mid, 
and  hind  brain,  may  be  seen  by  the  following  table  : 


TABULAR  VIEW  OF  THE  SUBDIVISIONS  OF  THE  VERTEBRATE  BRAIN. 

Olfactory  lobes  or  ganglia,  with  their  ventricles  (rhinen- 

cephalon). 

Cerebrum  or  cerebral  lobes  or    hem'spheres  (with  the 
Fore  brain  1          two  lateral  or  first  and  second  ventricles,  forming 

the  prosencephalon  or  prothalami). 

Optic  thalami,   with   the   third  ventricle  and  coriarium 
above   and   hypophysis   below  (Thalamencephalon  ; 
[         pineal  gland). 


NERVOUS  SYSTEM  OF    VERTEBRATES 


Hribmn. 


393 


f  Optic  lob.'S,  corpora  bigeniiua  or  quadrigemina  (mesen- 


cephalon). 


I  Optic  ventricle  or  Iter  a  tertio  ad  quartum  ventriculum. 


j  Cerebellum  (with  its  ventricle  and  the  pons  varolii,  form- 
Hind  brain.  \          ing  the  metencephalon). 

I  Medulla  oblongata  and  fourth  ventricle. 


The  accompanying  sketches  represent  the  typical  nervous 
system  of  an  amphibian,  which  also  resembles  that  of  many 
fishes,  and  even  the  lower  Reptilia. 

The  spinal  cord  (Fig.  374)  usually 
extends  through  the  whole  length  of 
the  spinal  canal,  except  in  the  toads 
and  frogs,  birds  and  many  mammals, 
where  it  stops  short  of  the  end  of  its 
canal.  In  those  Vertebrates  with 
limbs,  the  cord  enlarges  where  the 
nerves  which  supply  them  are  sent  off  ; 
these  are  the  cervical  or  thoracic,  and 
lumbar  enlargements,  especially  large 
in  turtles  and  birds.  The  white  and 
gray  substance  of  the  brain  continues 
in  the  cord. 

As  the  most  essential  characteristic 
of  Vertebrates  is  the  internal  skeleton 
(endoskeleton)  we  will  enter  more  into 
detail  in  describing  it,  and  afterwards 
notice  the  external  skeleton  (exo- 
skeleton). 

In  the  embryos  of  higher  Vertebrates 

and  in  the  adult  lancelet,  hag-fish  and  ]jeicerebell         the  form  of  a 
lamprey,  the  vertebral  column  is  rep-  lamella  bridging  over  the 

,   V  i  -,        i  fourth  ventricle  («)  ;  m,  spinal 

resented  by  a  rod-like  axis  (notochord  cord ;  t,  terminal  cord.-After 
or  chorda  dorsalis)  which  is  composed 
of  indifferent,  or  only  partly  organized  cells,  the  substance 
of  the  chord  resembling  cartilage.    These  chordal  cells  secrete 
a  membrane  called  the  chordal  sheath.    The  notochord  is  not 


ZOOLOGY. 


segmented.     In  all  Vertebrates  above  the  lamprey,  the  verte- 
bral column  grows  around   the   notochord,  which  finally 

JL 


FIG.  375. 


Fia.  376. 


Fig.  374.— Transverse  section  through  the  spinal  cord  of  a  calf.  «,  anterior,  £, 
posterior  longitudinal  fissure  ;  c,  central  canal ;  d,  anterior,  e,  posterior  cornua ;  /, 
eubstantia  gelatinosa ;  g,  anterior  column  of  the  white  substance  ;  A,  lateral,  i,  pos- 
terior column  ;  &,  transverse  commissures.  —After  Gegenbaur. 

Fig.  375.— Section  through  the  vertebral  column  of  Ammoccetes  (lamprey).  Ch,  no- 
tochord;  cs,  cbordal  sheath  ;  ra,  spinal  chord ;  a,  aorta;  v,  veins. 

Fig.  376.— Section  through  the  spinal  column  of  a  young  salmon.  Ch,  notochorcl  ; 
cs,  cnordal  sheath;  m,  spinal  chord;  k,  superior,  kf,  inferior  arch  (rudimentary) ;  a, 
aorta ;  »,  veins. — After  Gegenbaur. 

forms  the  central  portion  of  the  bodies  of  the  vertebrae,  and 
in  the  higher  Vertebrates  is  wholly  effaced ;  the  centra  or 


LIMBS  OF  VERTEBRATES. 


395 


Fig.  377.— Diagram  of  a  Vertebra 
with  its  body  (5),  rib  (7),  breast-bone 
(6)  ;  1,  neural  spine;  2,  3,  fore  and 
hind  oblique  processes  ;  4,  transverse 
processes. 


bodies  of  each  vertebra  of  a  lizard,  bird  or  mammal  being 

solid  bone.     Figs.  375  and  376  represent  the  relations  of  the 

notochord  in  an  adult  lamprey  and  a  young  fish. 
The  vertebra  of  a  bony  fish 

or   higher    vertebrate    consists 

of    a  body,   with   a   dorsal  or 

neural  spine ;  a  pair  of  oblique 

processes  (zygapophyses)  arching 

over  and  enclosing  the  spinal 

cord ;  and  transverse  processes, 

bending  downwards,  to  which 

the  ribs  are  articulated ;  certain 

of   the    thoracic    ribs    uniting 

with  the  sternum  or  breast-bone 

(Figs.  377  and  378.) 
Vertebrae  like  those  of  fishes, 

which  are  hollow  or  concave  at 

each  end,  are  said  to  be  amphicwlous  ;  those  hollow  in  front 

and  convex  behind  procwlous,  as  in  most  toads  and  frogs 

and  crocodiles,  and  most  existing 
lizards,  and  those  convex  in  front 
and  concave  behind  opisthoccelous, 
as  in  the  garpike,  some  Amphib- 
ians (the  salamanders  and  cer- 
tain toads,  Pipa  and  Bombinator). 
Vertebrates  never  have  more 

Pig.   378.— Thoracic  vertebra    of  . 

buzzard  (Buteo  vulgaris).  c,  centrum   than    two   pairs   01    limbs,    an   an- 
body :  s,  superior  spinous  pro-    .  ,  , .     ,  .         ,  -, 

to,  tenor  and  hinder  pair  ;  the  pecto- 
ral pair  of  fins  of  fishes  represent 
the  fore  limbs  of  Amphibians  and 
higher  Vertebrates,  and  the  arms  of  man ;  the  two  ventral 
fins  represent  the  hind  legs  of  higher  Vertebrates,  and  the 
legs  of  man.  Each  pair  of  limbs  is  connected  by  ligaments 
and  muscles  to  a  girdle  or  set  of  bones,  called  respectively 
the  shoulder  girdle  and  pelvic  girdle,  each  girdle  being  con- 
nected by  muscles  to  the  vertebral  column.  The  shoulder 
girdle  consists  of  a  clavicle  (or  collar-bone),  scapula  (or 
shoulder-blade),  and  coracoid  bone,  usually  a  process  of  the 
scapula.  These  bones  differ  greatly  in  the  different  classes, 


or 

cess ;  tr,  transverse  process 

rib  ;  a,  tuberculum  of  the  rib  :  $,  ca- 
pitulum  of  the  rib.-After  Gegen- 

baur- 


396 


ZOOLOGY. 


and  are  reduced  to. cartilaginous  pieces  in  sharks.  The  pelvic 
girdle,  or  pelvis,  consists  of  three  bones,  i.e.,  one  dorsal,  the 
ilium,  and  two  ventral,  the  anterior  of  which  is  called  pubis, 
and  the  posterior  ischium. 

The  limbs  each  consist  of  a  single  long  bone,  succeeded  by 
two  long  bones,  followed  by  two  transverse  rows  of  short 
wrist  or  ankle  bones,  and  five  series  of  long  finger  or  toe 
bones,  called  phalanges.  For  example,  in  the  fore  limb  of 
most  Vertebrates,  as  in  the  arm  of  man,  to  the  shoulder  gir- 
dle, i.e.,  at  the  point  of  junction  of  the  three  bones  com- 
posing it,  is  articulated  the  humerus ;  this  is  succeeded  by 


PIG.  379. 


Fio  380. 


FIG.  a81. 


Fig.  379.— Sternum  and  shoulder  girdle  of  Frog  (Sana 
temporarta).  p,  body  of  the  sternum ;  sc,  scapula ;  sc', 
supra-scapula ;  co,  coracoid  bone,  fused  in  the  middle  line 
with  its  fellow  of  the  opposite  side  (s) ;  cl,  clavicle ;  e,  epis- 
ternum.  The  extreme  shaded  double  portion  below  p  is  the 
xiphisternum.  The  cartilaginous  parts  are  shaded.— After 
Gegenbaur. 

Fig.  380.— Fore-leg  of  a  peal.  S,  scapula  ;  H^  humerus  ; 
0,  olecranon  or  tip  of  elbow  ;  It,  radius ;  Z7",  ulna ;  Po, 
pollex,  or  thumb. 

Fig.  381. — Pelvis  or  pelvic  bones  on  one  side  of  a  marsu- 

Sial  (Kangaroo).    62,  ilium;  a,  situated  on  the  pubic  bone 
wbis)  indicates  the  acetabulnm  or  concavity  for  the  artic- 
ulation of  the  head  of  the  femur ;  63,  iechium,  consolidated  with  the  pubis.    The 
three  bones  thus  consolidated  form  the  os  innominatum ;  m,  marsupial  bones  ar- 
ticulated to  the  pubic  bones.  —After  Owen. 

the  ulna  and  radius,  the  wrist-bones  or  carpals,  and  the  fin- 
ger-bones or  phalanges,  the  single  row  of  phalanges  forming 
a  digit  (finger  or  toe).  To  the  point  of  union  (acetabulum, 
Fig.  381,  a)  of  the  three  pelvic  bones  is  articulated  the  fe- 
mur, or  thigh;  this  is  succeeded  by  the  tibia  and  fibula 
(shank-bones),  the  tarsal  and  metatarsal  bones  (ankle-bones), 
and  the  phalanges  or  bones  forming  the  digits  (toes). 

Figs.  383-385  represent  the  simplest  form  of  the  posterior 
limbs  in  the  higher  Vertebrates,  that  of  the  bird  showing  an 


COMPOSITION  OF  THE  SKULL. 


399 


ing  gill-slits  or  spiracles,  but  are  closed  in  the  higher  Verte- 
brates. As  a  rule,  the  skull  is  symmetrical,  exceptions  being 
found  in  the  flounders  and  the  bones  about  the  nose  of  cer- 


Fig.  386.- Skull  of  the  Lion.  2,  occipital  condyle  ;  7,  Parietal  bone  and  sagittal 
crest ;  8,  p&roccipital ;  27',  squamosal  bone  ;  27,  zygomatic  arch  ;  26,  malar  bone  ; 
11,  frontal  bone ;  12,  post-orbital  process;  15,  nasal  bone;  21,  maxillary  bone;  22, 
premaxillary  bone  ;  32,  mandible  ;  3,  occipital  crest ;  c,  canine  teeth  ;  />a,  second  pre- 
molar  ;  ml,  molar  tooth. — After  Owen. 

tain  whales  and  porpoises.  The  base  of  the  skull  is  perfo- 
rated for  the  exit  of  the  nerves  proceeding  from  the  base  of 
the  brain,  and  the  hinder  bone  (occiput)  is  perforated  (fora- 
men magnum)  for 
the  passage  of  the 
spinal  cord  from  the 
medulla  oblongata. 
It  is  probable  that 
there  is  a  general 
parellelism  between 
the  head  of  Insects 
a  n  d  Vertebrates, 

i.e..  that  while   the  Fig.  387.— Skull  and  visceral  skeleton  of  a  Selachian 

_  (diagram),    occ,  occipital  region;  la,  wall  of  the  laby- 

head  OI  insects,  for  rinth  ;  eth,  ethmoidal  region  ;  n,  nasal  pit ;  a,  first,  b,  c, 

,                 .    .        „  second  labial  cartilage  ;  o,  superior,  n,  inferior  portion 

example,  Consists  OI  of  the  mandibular  arch  7. ;  //.,  hyoid  arch  ;  III. -VIII. 

a  certain  number  of  (1'6)' branchial  arches-After  <**»*««• 
segments,  homologous  with  those  of  the  rest  of  the  body, 
and  with  mouth-parts  homologous  with  the  limbs  ;  that  the 
skull  is  also  segmented,  and  an  expansion  and  continuation 
of  the  vertebral  column.  Gegenbaur  even  maintains  that 
the  various  arches  of  the  head  are  homologous  with  the  limbs. 


400  ZOOLOGY. 

On  the  other  hand,  while  the  brain  of  insects  is  a  single 
pair  of  ganglia  like  those  of  the  rest  of  the  body,  the  differ- 
ent ganglia  forming  the  brain  of  Vertebrates  are  concen- 
trated in  the  head  alone  ;  still  the  different  pairs  of  nerves 
sent  off  from  the  base  of  the  brain  are  homologous  with 
the  spinal  nerves,  sent  off  at  intervals  corresponding  to  each 
vertebra. 

There  are  two  theories  of  the  composition  of  the  skull. 
That  of  Oken,  Goethe,  and  of  Owen,  who  believed  that  the 
skulls  of  the  bony  fishes  and  mammals  were  composed  of 
three  or  four  segments.  It  should  be  noticed  that  these 
views  are  based  on  an  examination  of  highly  specialized  ver- 
tebrates. From  a  study,  however,  of  the  more  generalized 
types  of  fishes  (such  as  the  sharks),  and  the  embryos  of  ver- 
tebrates belonging  to  different  groups,  the  old  vertebrate 
theory  of  the  skull  has  been  discarded,  and  the  view  of  Ge- 
genbaur,  confirmed  by  Salensky,  is  probably  nearly  the  cor- 
rect one.  As  stated  by  Gegenbaur  : 

1.  The  skull  is  comparable  to  a  portion  of  the  vertebral 
column,  which  contains  at  least  as  many  vertebral  segments 
as  there  are  branchial  arches.    This  view  is  borne  out  by  the 
following  facts  : 

a.  The  notochord,  which  forms  the  foundation  of  the 

vertebral  column,  passes  through  the  cranium  in  the 
same  way  as  it  passes  through  the  vertebral  column. 

b.  All  the  nerves  which  pass  out  of  the  base  of  the 

skull  (or  that  portion  traversed  by  the  notochord) 
are  homologous  with  the  spinal  nerves. 

c.  The  difference  between  the  skull  and  vertebral  col- 

umn consist  of  secondary  adaptations  to  certain  con- 
ditions, which  are  external  to  the  skull,  and  are 
partly  due  to  the  development  of  a  brain. 

2.  The  skull  may  be  divided  into  two  regions,  a  vertebral 
portion   and   an   anterior  evertebral   portion,  lying  beyond 
the  end  of  the  notochord. 

3.  The  number  of  vertebrae  which  enter  into  the  forma- 
tion of  the  skull  are  nine  at  least  (according  to  Salensky,  in 
the  sturgeon,  seven) ;  the  exact  number  is  immaterial. 


TEETH  OF  VERTEBRATES.  401 

In  the  lancelet  there  is  no  skull,  or  even  the  rudiments  of 
one  (unless  the  semi-cartilaginous  supports  of  the  tentacles 
be  regarded  as  such),  hence  the  Vertebrates  are  divided  into 
the  skulless  or  acraniate  (Acrania,  represented  by  the  lance- 
let  alone)  and  the  skulled  or  craniate  (Craniota},  the  latter 
series  comprising  all  forms  from  the  hag-fish  to  man.  In 
the  Craniota  the  skulls  may  be,  according  to  Gegenbaur,  di- 
vided into  two  groups.  In  the  hag  and  lamprey  the  noto- 
chord  is  continued  into  the  base  of  a  small  cartilaginous 
capsule,  enclosing  the  brain,  and  which  represents  the  skull 
of  higher  Vertebrates  (Craniota).  This  capsule  behind  is 
continuous  with  the  spinal  column. 

With  the  skull  of  the  second  form  two  jaws  are  developed, 
hence  all  the  vertebrates  above  the  hag  and  lamprey  form  a 
series  (Gnatliostomata]  opposed  to  the  former,  or  Cyclos- 
tomato. 

In  the  Gnatliostomata  there  is  a  gradual  modification  and 
perfection  of  the  skull.  In  the  sharks  it  may  be  quite  sim- 
ple and  cartilaginous  ;  in  the  bony  fishes  it  is  highly  special- 
ized, consisting  of  a  large  number  of  separate  bones.  In 
the  Amphibians  we  first  meet  with  a  skull  consisting  of  few 
bones,  easily  comparable  with  those  of  mammals ;  in  the 
reptiles  and  birds  the  ear-bones  are  external,  forming  the 
large  quadrate-bone  by  which  the  lower  jaw  is  articulated  to 
the  skull.  A  progress  is  seen  in  the  mammals  where  the 
quadrate-bone  becomes  internal — one  of  the  ear-bones  (the 
incus).  Now  also,  the  brain  becoming  much  larger,  evincing 
a  much  higher  grade  of  intellect,  the  skull  is  greatly  en- 
larged to  accommodate  the  great  increase  in  size  of  the 
cerebrum  and  cerebellum,  the  perceptive  and  reasoning  fac- 
ulties predominating  over  those  regions  of  the  brain  and 
skull  devoted  to  perceiving,  grasping,  and  masticating  the 
food. 

Though  not  properly  forming  part  of  the  skeleton  or  de- 
veloped with  it,  we  may  here  consider  the  teeth. 

The  teeth  of  Vertebrates  are  formed  from  the  modified 
epidermis  and  cutis,  or  dermis ;  the  former  secretes  the 
enamel  and  the  latter  is  changed  into  the  pulp  or  dentine. 
The  simplest  form  of  tooth  is  conical.  In  the  jawless  hag 
there  are  no  teeth  in  the  lips,  but  a  single  median  tooth  on 


40^  ZOOLOGY. 

the  palate  and  two  rows  of  comb-like  teeth  on  the  tongue. 
In  the  lamprey  the  edges  of  the  circular  mouth  are  provided 
with  circular  rows  of  conical  horny  teeth.  The  teeth  of 
higher  Vertebrates  are  derived  from  the  cells  of  the  mucous 
membrane  of  the  mouth,  which  is  formed  of  connective  tis- 
sue as  well  as  epithelium.  The  teeth  of  fishes  are  developed 
not  only  in  one  or  several  rows  in  the  lip,  but  may  also  arm 
the  bony  projections  into  the  mouth-cavity  of  the  palate, 
vomer  and  parasphenoid  bones  and  the  hyoid  and  bran- 
chial arches.  In  the  Amphibia  teeth  survive  on  the  palatine 
and  vomerine  bones,  more  rarely  on  the  parasphenoid  ;  among 
the  reptiles,  the  snakes  and  lizards  alone  have  teeth  on  the 
palatine  and  pterygoid  bones,  while  in  the  crocodiles  and  in 
mammals  the  teeth  are  confined  to  the  maxillary  bones.  In 
the  geckos,  snakes  and  the  crocodiles,  as  well  as  the  mam- 
mals, the  teeth  are  inserted  in  sockets  (alveoli)  of  the  jaw. 
(Gegenbaur. ) 

In  certain  extinct  birds  (Odontornithes)  there  were  teeth 
in  the  jaws,  though  all  existing  birds  are  toothless.     It  is 

said  that  rudimentary 
teeth  were  found  by 
Geoffrey  St.  Hilaire  in 
the  jaws  of  a  parrot. 
Blanchard  afterwards 
found  the  germs  of 
teeth  there,  though 
they  never  come 
through.  In  the  Mam- 
mals the  teeth  are  dif- 

Fig.  383.— Teeth  of  the  Tasmanian  devil.    The  ferentiated     into 
incisors  are  situated  in  front  of  the  large  conical  ™™™c,       - 

canine  teeth.    2,  3,  premolars  ;  m,  1-4,  four  molar  SOrS,     Canines,      p 

teeth.-AfterOwen.  ]arg    and    molars     (Fig. 

383).  In  descriptive  anatomy  the  teeth  are  for  convenience 
expressed  by  a  formula,  the  number  of  teeth  of  the  upper 
jaws  being  placed  like  the  numerator  of  a  fraction,  and  those 
of  the  lower  jaw  like  the  denominator,  the  initials  of  the 
names  of  the  teeth  being  placed  before  the  figures,  thus 

the  dental  formula  of  man  is  1^.  cl=±;P  |=|,  M*~ 

#  —  .</  1  —  1  6  —  <i  O  —  O 


SCALES,  HAIRS,  AND 


FEATHERS^  '     ^ 


403 


In  the  fishes,  Amphibians  and  reptiles,  the  worn-out  teeth 
are  replaced  by  a  succession  of  new  ones  ;  in  mammals  (ex- 
cept cetaceans,  where  there  is  no  change)  there  is  but  a  single 
change,  the  first  (milk)  teeth  being  replaced  by  a  second  set      • 
of  permanent  teeth.     The  teeth  of  the  lower  Vertebrates      .- 
are  shed  while  swallowing  the  food.     In  the  boa  (Python) 
the  teeth  thus  shed  are  found  scattered  along  the  intestinal 
canal  and  are  discharged  with  the  remnants  of  the  food 
(Wyman). 

The  dermal  or  exoskeleton  consists  of  the  scales  of  fishes, 
reptiles  and  certain  mammals,  such  as  the  armadillo,  the 


Fig.  384.— Vertical  section  through  the  skin  of  an  embryonic  shark.  C,  corium  or 
dermis  ;  c,  c,  c,  layers  of  the  corium  ;  d,  uppermost  layer  ;  p,  papilla  ;  E,  epidermis ; 
e,  its  layer  of  columnar  cells ;  0,  enamel  layer.— After  Gegenbaur. 

feathers  of  birds  and  the  hairs  of  mammals.  Most  scales 
arise  from  dermal  papillae  (Fig.  384,^?),  and  are  covered  over 
by  a  layer  of  enamel  (Fig.  384,  o)  developed  from  the  epider- 
mis ;  so  that  the  scales  of  sharks  and  rays,  and  turtles, 
arise  from  both  the  dermis  and  epidermis. 

A  hair  or  feather  is  a  modification  of  a  scale  ;  the  papilla 
is  sunken  in  a  pit  of  the  dermis,  the  conical  cap  of  epi- 
dermis arising  from  it  ultimately  forming  the  hair  or  feather. 
The  plates  of  turtles,  the  scales  of  snakes  and  lizards,  and 
feathers  of  birds  are  epidermal.  In  the  horns  of  mammals, 
as  of  the  rhinoceros,  and  the  hoofs  of  the  horse,  the  epi- 
dermal substance  is  penetrated  by  numerous  long  dermal 
papillae. 


404 


ZOOLOGY. 


The  head  of  the  sturgeon,  garpike,  and  of  other  ganoid 
fishes,  is  protected  by  solid  dermal  bones,  and  the  shells  of 
turtles  are  dermal  structures. 

The  color  of  the  skin  of  Vertebrates  is  due  to  pigment- 
granules  situated  either  in  the  epidermis  or  dermis,  and  in 

the  chameleon  they 
are  contained  in  special 
sacs  (chromatophores) 
which  are  under  the 
control  of  the  nervous 
system. 

The  muscular  system 
of  Vertebrates  arises 
from  the  middle  germ- 
layer  (mesoderm),  and 

Fig.  385.—  Placoid  scale  of  dog-fish  (vertical  sec-  •  41.  ..  _.»_-„  i.\^n  Yvmo/Vloc. 
tiqn  magnified).  a,  enamel  layer  ;  6,  dentine  of  the  m  "-he  germ  the  muscles 
spine  on  the  scale.-After  Owen.  jn  part  a^ge  f  rom  ^e 

primary  segments  indicated  by  the  protovertebrae,  while  in 

the  adults  of  fishes  and  certain  salamanders,  the  muscular 

system  is  distinctly  segmented,  corresponding  to  the  seg- 

mentation of  the  ver- 

tebral    column,    the 

four     lateral     trunk- 

muscles  being  divided 

into  a  number  of  seg- 

ments   by  tendinous 

bands,   which    corre- 

spond in  number  to 

the  vertebrae  (Gegen- 

baur). 

The  eye  in  Verte- 
brates in  its  develop- 
mentalhistorybelongs 
to  a  different  type  of 
structure  from  that  of 

any  invertebrates,  im 
less    it    be    the    larval 


-CyHM  scale  of  roach,  magnified,  seen  in 
>  and  from  tne  surface,  B.—  After  Owen. 


Ascidians,  for  in  both  types  the  eye  is  said  by  Gegenbaur  not 
to  be  ^directly  developed  from  the  ectoderm,  but  from  the 


ETE8  AND  EARS  OF  VERTEBRATES.  405 

anterior  portion  of  the  central  nervous  system.  The  differ- 
ence between  the  highly-developed  eye  of  a  cuttle-fish  and 
a  bony  fish,  for  example,  consists  in  the  fact  that  the  rods 
and  cones  (similar  to  those  of  the  invertebrate  eye)  forming 
a  layer  (the  bacillar  layer)  behind  the  retina,  are  in  the  ver- 
tebrate eye  turned  away  from,  while  in  the  invertebrates  they 
are  directed  toward  the  opening  of  the  eye. 

The  ear  of  Vertebrates  is  at  first  a  primitive  otocyst,  or 
ear- vesicle,  which  is  gradually  cut  off  and  enclosed,  forming 
a  cavity  of  the  skull.  As  we  rise  towards  the  mammals,  the 
ear  becomes  more  and  more  developed  until  the  inner, 
middle,  and  outer  ear  is  formed  ;  the  Eustachian  tube  being  a 
modification  of  the  first  branchial  cleft,  forming  the  spiracle 
in  the  sharks  (Selachii)  and  Ganoids. 

In  the  lancelet  a  head  is  scarcely  more  set  apart  from  the 
rest  of  the  body  than  in  many  invertebrates.  In  the  fishes 
and  Amphibians  the  head  is  not  separated  by  a  neck  from 
the  trunk  ;  in  reptiles  the  neck  begins  to  mark  off  a  head 
from  the  thorax,  while  in  the  birds  and  mammals  the  head 
is  clearly  demarked,  the  degrees  of  cephalization  and  trans- 
fer headward  of  those  features  subordinate  to  the  intellec- 
tual wants  of  the  animal  becoming  more  striking  as  we 
ascend  through  the  mammalian  series  to  the  apes,  and  finally 
man. 

The  development  of  Vertebrates  can  scarcely  be  epitomized 
in  a  few  lines.  The  mode  of  growth  of  Amphioxus  is  a 
general  expression  for  that  of  all  Vertebrates,  for  all  develop 
from  fertilized  eggs,  which  undergo  total  or  partial  segmen- 
tation of  the  yolk,  become  three-layered  sacs  and  assume  the 
peculiar  vertebrate  characters,  the  development  of  the  mam- 
mals differing  from  that  of  the  other  classes  only  in  compar- 
atively unimportant  features. 

The  Vertebrates  are  divided  into  two  series  or  sub-branches: 
the  Acrania  and  Craniota  ;  the  former  type  is  represented 
by  but  a  single  genus,  order  and  class,  the  lancelet  or  Am- 
phioxus. The  sub-branch  Craniotais  divided  into  six  class- 
es, the  Marsipobranchs,  fishes,  amphibians,  reptilia,  birds 
and  mammals. 


406 


ZOOLOGY. 


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CLASS  1.  LEPTOCARDII  (Lancelet). 

The  lancelet  is  the  only  type  of  this  class.  From  its 
worm-like  form  it  was  regarded  as  a  worm  by  some  authors, 
and  as  a  mollusk  ("Limax")  by 
Pallas.  The  body  is  four  or  five  cen- 
timetres in  length,  slender,  com- 
pressed, pointed  at  each  end,  hence 
the  generic  name  (Amphioxus,  aj^cpt, 
both,  o£t>s,  sharp),  the  head-end  be- 
ing thin,  compressed.  The  muscu- 
lar segments  are  distinct  to  the 
naked  eye.  From  the  mouth  to  the 
vent  is  a  deep  ventral  furrow,  and 
a  slight  fin  extends  along  the  back 
and  ventrally  as  far  front  as  the  vent. 

The  lancelet,  A.  lanceolatus  (Pal- 
las), lives  in  sand  just  below  low- 
water  mark,  ranging  on  our  coast  from 
the  mouth  of  Chesapeake  Bay  to 
Florida ;  it  also  occurs  on  the  South 
American  coast,  and  in  the  European 
seas  and  the  East  Indies,  the  species 
being  nearly  cosmopolitan. 

As  this  is  the  lowest  Vertebrate,  its 
structure  and  mode  of  development 
merit  careful  study. 

The  mouth  is  oval,  surrounded 
with  a  circle  of  ciliated  tentacles 
supported  by  semi-cartilaginous  pro- 
cesses arising  from  a  circumoral  ring. 
The  mouth  leads  directly  into  a  large 
broad  pharynx  or  "branchial  sac" 
(Fig.  387,  d),  protected  at  the  en- 
trance by  a  number  of  minute  cili- 
ated lobes. 

The  walls  of  this  sac  are  perforated 
by  long  ciliated  slits,  comparable  with  those  of  the  bran- 


DEVELOPMENT  OF  THE  LANCELET.  407 

chial  sacs  of  Ascidians  and  of  Balanoglossus.  The  water 
which  enters  the  mouth  passes  out  through  these  slits  when 
it  oxygenates  the  blood,  and  enters  the  general  body-cavity, 
thence  passing  out  of  the  body  through  the  abdominal  pore 
(Fig.  387,  c).  The  pharynx  leads  to  the  stomach  (e),  with 
which  is  connected  the  liver  or  coscum  (/).  There  is  a 
pulsatile  vessel  or  tubular  heart,  beginning  at  the  free  end 
of  the  liver,  and  extending  along  the  underside  of  the  phar- 
ynx, sending  branches  to  the  sac  and  the  two  anterior  branches 
to  the  dorsal  aorta.  "  On  the  dorsal  side  of  the  pharynx  the 
blood  is  poured  by  the  two  anterior  trunks,  and  by  the 
branchial  veins  which  carry  away  the  aerated  blood  from 
the  branchial  bars,  into  a  great  longitudinal  trunk  or  dorsal 
aorta,  by  which  it  is  distributed  throughout  the  body." 
(Huxley.)  There  are  also  vessels  distributed  to  the  liver, 
and  returning  vessels,  representing  the  portal  and  hepatic 
veins.  The  blood-corpuscles  are  white  and  nucleated. 

The  vertebral  column  is  represented  by  a  notochord  which 
extends  to  the  end  of  the  head  far  in  front  of  the  nervous 
cord  ;  and  also  by  a  series  of  small  semi-cartilaginous  bodies 
above  the  nervous  system,  and  which  are  thought  to  repre- 
sent either  neural  spines  or  fin-rays.  The  nervous  cord  lies 
over  the  notochord  ;  it  is  not  divided  into  a  true  brain*  and 
spinal  cord,  but  sends  off  a  few  nerves  to  the  periphery,  with 
nerves  to  the  two  minute  eye-spots.  There  are  no  kidneys 
like  those  of  the  higher  Vertebrates,  but  glandular  bodies 
which  may  serve  as  such.  The  reproductive  glands  are 
square  masses  attached  in  a  row  on  each  side  of  the  walls  of 
the  body-cavity.  The  eggs  may  pass  out  of  the  mouth  or 
through  the  pore.  Ko walevsky  found  the  eggs  issuing  in 
May  from  the  mouth  of  the  female,  and  fertilized  by  sper- 
matic particles  likewise  issuing  from  the  mouth  of  the  male. 
The  eggs  are  very  small,  0  •  105  millimetres  in  diameter.  The 
eggs  undergo  total  segmentation,  leaving  a  segmentation- 
cavity  which  becomes  the  body-cavity. 

The  blastoderm  now  invaginates  and  the  embryo  swims 
about  as  a  ciliated  gastrula.  The  body  is  oval,  and  the  germ 
does  not  differ  much  in  appearance  from  a  worm,  starfish, 
*  Langerhans  has  figured  an  olfactory  lobe;  and  all  observers  agree 
that  a  ventricle  is  present  ;  thus  there  is  a  slight  approximation  to  a 
brain. 


408  ZOOLOGY. 

or  ascidian  in  the  same  stage  of  growth.  No  vertebrate 
features  are  yet  developed. 

Soon  the  lively  ciliated  gastrula  elongates,  the  alimentary 
tube  arises  from  the  primitive  gastrula-cavity,  while  the  edges 
of  the  flattened  side  of  the  body  grow  up  as  ridges  which 
afterwards,  as  in  all  vertebrate  embryos,  grow  over  and  en- 
close the  spinal  cord.  When  the  germ  is  twenty-four  hours 
old  it  assumes  the  form  of  a  ciliated  flattened  cylinder,  and 
now  resembles  an  Ascidian  embryo  (Fig.  138,  B),  there 
being  a  nerve-cavity,  with  an  external  opening,  which  after- 
wards closes.  The  notochord  appears  at  this  time. 

In  the  next  stage  observed  the  adult  characters  had  ap- 
peared, the  mouth  is  formed,  the  first  pair  of  gill-openings 
are  seen,  eleven  additional  pairs  appearing.  It  thus  appears 
that  while  the  lancelet  at  one  time  in  its  life  presents  Ascidian 
features,  yet  as  Balfour  states  "  all  the  modes  of  develop- 
ment found  in  the  higher  Vertebrates  are  to  be  looked  upon 
as  modifications  of  that  of  Amphioxus." 

A  second  form  of  this  group,  from  Moreton  Bay,  North- 
ern Australia,  has  been  described  by  Peters  under  the  name 
of  Epigonichtliys  cultellus.  It  differs  from  Amphioxus  in 
the  presence  of  a  high  dorsal  fin,  in  the  want  of  a  distinct 
caudal  and  anal  fin,  with  some  differences  in  the  structure 
of  the  mouth  and  oral  tentacles.  It  is  from  thirteen  to 
twenty-three  millimetres  in  length. 


CLASS  I.—  LEPTOCARDII. 

Comprising  the  lowest  Vertebrate  known  ;  body  lancet-shaped,  with  no 
skeleton;  notochord  persistent,  no  brain;  no  cranium  ;  no  paired  fins  ; 
blood  colorless  ;  a  metamorphosis  ;  gastrula  ciliated,  free-swimming. 

A  single  order  (Pharyugobranclii),  family  (Amphioxini),  and  genus 
(Amphioxus),  each  with  the  characters  of  the  class. 

Laboratory  Work. — The  structure  of  the  lancelet  can  only  be  imper- 
fectly made  out  by  a  triplet  lens  and  higher  powers  ;  but  by  sections 
stained  with  carmine  the  anatomy  can  be  well  studied.  Brooks  has 
found  tbe  young  in  the  later  free-swimming  stages  on  the  surface  of 
tho  ocean  near  Fortress  Monroe. 


GENERAL  CHARACTERS  OF  MARS1POBRANCH8.    409 


CLASS  II.  MARSIPOBRA^CHII  (Lampreys,  or  Cydostomi). 

General  Characters  of  the  Cyclostomatous  Vertebrates. 
— In  the  hag-fish  and  lamprey,  representatives  of  the  jaw- 
less  Vertebrates,  the  body  is  long  and  slender,  cylindrical, 
the  skin  smooth,  scaleless,  with  only  a  median  dorsal  and 
ventral  fin  (or  in  Myxine  only  a  small  lower  median  fin)  ; 
the  mouth  is  circular,  and  in  the  lampreys  armed  with  nu- 
merous conical  teeth.  There  is  no  bony  skeleton ;  the 
spinal  column  is  represented  simply  by  a  thick  rod  (dorsal 
cord,  notochord)  surrounded  by  a  sheath.  The  skull  is  car- 
tilaginous, not  movable  on  the  vertebral  column ;  is  very 
imperfectly  developed,  having  no  jaws,  the  hyo-mandibu- 
lar  bones  and  the  hyoid  arch  existing  in  a  very  rudimentary 
state.  The  few  teeth  present  in  the  hag-fish  are  confined  to 
the  palate  and  tongue  ;  those  of  the  lamprey  are  numerous, 
conical  and  developed  on  the  cartilages  supporting  the  lips. 

The  nervous  system  is  much  as  in  the  fishes,  the  brain 
with  its  olfactory,  cerebral  lobes,  thalami,  optic  lobes,  and 
medulla  being  developed,  the  cerebellum  in  Myxine  blended 
Avitb,  in  the  lamprey  free  from  the  medulla.  The  digestive 
canal  is  straight,  with  no  genuine  stomach,  but  the  liver  is 
much  as  in  higher  Vertebrates.  The  respiratory  organs  are 
very  peculiar,  being  purse-like  cavities  (whence  the  name 
Marsipobranchii),  in  the  lamprey  being  seven  in  number  on 
each  side  of  the  pharynx,  opening  externally  by  small  aper- 
tures ;  internally  they  connect  with  a  long  cavity  lying  under 
the  oesophagus,  and  opening  anteriorly  into  the  mouth.  The 
heart  is  like  that  of  fishes,  as  are  the  kidneys.  The  eyes 
are  minute,  sunken  in  the  head  and  under  the  skin  in  the 
hag  (Myxine),  but  larger  in  the  lamprey. 

Another  extraordinary  feature  in  the  class  is  the  single 
nasal  aperture,  as  opposed  to  the  two  occurring  in  all 
higher  Vertebrates.  The  aperture  leads  to  a  sac,  which 
in  the  Myxine  communicates  with  the  mouth  (pharynx),  but 
in  the  lamprey  forms  a  cul-de-sac. 

The  ovaries  and  male  glands  (the  sexes  being  distinct)  are 
impaired  plates  suspended  from  the  back-bone,  and  have  no 


410  ZOOLOGY. 

ducts,  the  eggs  breaking  through  the  walls  of  the  ovary,  fall- 
ing into  the  abdominal  cavity  and  passing  out  of  the  abdom- 
inal pore.  The  eggs  of  Myxine  are  very  large  in  proportion 
to  the  fish,  enclosed  in  a  horny  shell,  with  a  filament  at  each 
end  by  which  it  may  adhere  to  objects. 

The  hag-fish  is  about  a  foot  long  and  an  inch  thick,  with 
the  head  small,  a  median  palatine  tooth,  and  two  comb-like 
rows  of  teeth  on  the  tongue.  There  is  a  single  gill-opening 
a  long  ways  behind  the  head ;  there  are  large  mucous  or 
slime-glands  on  the  side  of  the  body,  for  these  fishes  are 
very  slimy.  The  hag  lives  at  considerable  depths  in  the  sea  ; 
we  have  dredged  one  at  114  fathoms  in  soft  deep  mud  off 
Cape  Ann.  It  is  often  parasitic,  attaching  itself  to  the  bod- 
ies of  fish,  and  has  been  found  to  have  made  its  way  into  the 
body-cavity  of  sturgeons  and  haddock. 

The  lamprey  lives  both  in  fresh  and  salt  water.  The  eggs 
of  the  common  lamprey,  Petromyzon  marinus  (Linn.),  are 
laid  in  early  spring,  the  fish  following  the  shad  up  the  rivers, 
and  spawning  in  fresh  water,  seeking  the  sea  in  autumn  ; 
small  individuals,  from  five  to  seven  inches  long,  have  been 
seen  by  Dr.  Abbott  attached  to  the  bellies  of  shad,  sucking 
the  eggs  out  of  the  oviducts. 

The  lamprey  when  six  inches  long  is  quite  unlike  the  adult, 
being  blind,  the  eyes  being  concealed  by  the  skin  ;  it  is  tooth- 
less, and  has  other  peculiarities.  It  is  so  strangely  unlike  the 
adult  that  it  was  described  as  a  different  genus  (Ammoccetes). 
P.  nigricans  Lesueur  is  smaller,  and  occurs  in  the  lakes  of 
New  York  and  eastward,  while  P.  niger  Rafinesque  is  still 
smaller,  and  lives  in  the  "Western  States. 


CLASS  II.  MARSIPOBRANCHT. 

Worm-like  Vertebrates,  without  paired  fins  ;  notochorcl  persistent ;  a 
single  nasal  sac,  six  or  ten  pairs  of  purse-like  gill-sacs,  no  jaw-bones. 

Order  1.  Hyperotetra.—'NfLssil  duct  leading  into  the  mouth.     (Myxine.) 

Order  2.  Hyperoartia. — Nasal  duct  a  blind  sac,  not  connecting  with 
the  mouth.     (Petromyzon.) 


GENERAL  CHARACTERS  OF  FISHES.  411 

Laboratory  Work. — The  anatomy  of  these  animals  is  exceedingly  in- 
teresting ;  the  respiratory  sacs  and  nasal  duct  can  be  exposed  by  a  lon- 
gitudinal section  of  the  head  ;  the  relations  of  the  notochord  can  be 
best  seen  by  transverse  sections  ;  the  heart  and  vessels  should  be  in- 
jected. Preparations  of  the  brain  should  be  made,  and  with  care  the 
skull  prepared. 


CLASS  III.  PISCES  (Sharks,  Rays,  Sturgeons,  Garpikes,  and 
bony  fishes). 

General  Characters  of  Pishes. — We  now  come  to  Verte- 
brates which  have  genuine  jaw-bones  and  paired  fins,  and 
which,  in  short,  are  affiliated  to  the  Batrachians,  and  through 
them  with  the  reptiles,  birds,  and  mammals.  All  the  fishes 
agree  in  having  a  true  skull,  to  which  is  attached  a  movable 
lower  jaw.  The  brain  is  well  developed,  with  its  lobes  for 
the  most  part,  at  least,  equivalent  to  or  homologous  with 
those  of  the  reptiles,  birds,  and  mammals,  though  the  cere- 
bral hemispheres  are  small,  and  in  most  fishes  of  nearly  the 
same  size  as  the  optic  lobes  ;  the  cerebellum  is  also  generally 

Dorsal  fin. 


Caudal. 


Anal.       Ventral.        Pectoral. 
Fig.  388. -The  Mud-Minnow. 

of  moderate  size.  The  head  forms  part  of  the  trunk,  there 
being  no  neck  (except  in  the  Hippocampida),  and  the  body 
is  usually  compressed  and  adapted  in  shape  for  rapid  motion 
in  the  water. 

Paired  fins  are  always  primitively  developed,  though  the 
posterior  or  ventral  fins,  at  least,  are  in  many  cases  wanting 
through  the  atrophy  of  parts  developed  in  embryonic  life. 
The  pectoral  and  ventral  fins  (Fig.  388),  which  represent  the 
fore  and  hind  legs  of  higher  Vertebrates,  are  attached  to  the 
body  or  trunk  by  a  shoulder  and  pelvic  girdle.  The  shoulder 


412  ZOOLOGY. 

girdle  is  either  lyre-shaped  or  forked,  like  a  bird's  wish-bone, 
curved  forward,  and  with  each  side  connected  below ;  the 
fishes  in  this  respect  differing  from  the  Batrachians  (Gill). 
The  shoulder  girdle  is  usually  closely  connected  by  a  series 
of  intervening  bones  with  the  skull,  and  makes  its  first  ap- 
pearance opposite  the  interval  between  the  second  and  third 
vertebrae. 

The  skull  and  skeleton  may  be  either  cartilaginous  or  bony, 
and  the  bones  of  the  head  and  skeleton  very  numerous.  In 
some  sharks  there  are  365  vertebras  ;  in  some  bony  fishes  200, 
while  in  the  PlectognatM  (fishes  like  the  sun-fishes  and  Ba- 
listes)  there  may  be  no  more  than  fifteen  ;  thus  in  some 
fishes  there  may  be  about  one  thousand  separate  bones.  No 
fishes  have  a  well-defined  sternum  or  breast-bone,  this  bone 
appearing  for  the  first  time  in  the  Batrachians.  The  verte- 
bras are  almost  always  biconcave  ;  this  is  the  simplest,  most 
primitive  form  of  vertebra  ;  it  forms  a  weak  articulation, 
admitting,  as  Marsh  states,  of  free,  but  limited  motion. 

All  fishes  breathe  by  gills,  which  are  supported  generally 
on  four  or  five  cartilaginous  or  bony  supports  or  arches.  The 
gills  are  never  purse-shaped,  as  in  the  lampreys,  and  are 
mostly  situated  within  the  head,  in  front  of  the  scapular  arch. 

The  mouth  is  generally  armed  with  teeth  varying  greatly 
in  number  and  form,  and  in  the  bony  fishes  especially,  not 
only  the  jaws,  but  any  bony  projections,  such  as  the  palatine, 
pterygoid  and  vomerine  bones,  as  well  as  the  tongue  and  pha- 
ryngeal  bones  may  be  armed  with  teeth,  so  that  the  food  is 
retained  in  the  mouth  and  more  or  less  torn  and  crushed  be- 
fore being  swallowed. 

Fish  have  no  salivary  glands.  The  tongue  moves  only  as 
a  part  of  the  hyoid  apparatus  upon  which  it  is  attached. 
After  being  crushed  and  torn  in  the  mouth  the  food  passes 
through  a  short  throat  or  oesophagus  into  the  stomach.  The 
intestine  is  generally  provided  at  the  anterior  end  with 
several  or  numerous  ccecal  appendages  which  are  especially 
abundant  in  the  cod.  The  gut  is  twisted  once  or  twice  be- 
fore reaching  the  vent,  but  is  usually  much  shorter  than  in 
the  air-breathing  Vertebrates,  while  the  vent  is  placed  much 
nearer  the  mouth  than  in  the  tailed  Amphibians,  thus  sepa- 


STRUCTURE  OF  FISHES.  413 

rating  the  trunk  into  a  thoracic  and  caudal  portion.  To 
make  up  for  the  short  intestine,  its  absorbing  surface  is 
greatly  increased  in  all  except  the  bony  fishes  by  a  peculiar 
fold  called  the  "spiral  valve."  The  rectum  always  opens  in 
front  of  the  urinary  and  genital  outlets  ;  except  when  the 
latter  communicates  directly  with  the  rectum,  thus  forming 
a  cloaca.  All  fishes  have  a  well-developed  liver,  usually  a  gall- 
bladder, with  several  gall-ducts  ;  and  in  general  a  yellowish 
pancreas. 

The  heart  consists  of  a  ventricle  and  auricle,  the  latter 
branchial  with  a  venous  sinus  (sinus  venosus)  ;  while  to  the 
ventricle  is  added  an  arterial  bulb,  which  subdivides  into  five 
pairs  of  arteries,  one  for  each  gill-arch.  The  Dipnoi  ap- 
proach the  Amphibians  in  the  possession  of  a  second  auricle 
as  well  as  of  genuine  lungs,  i.e.,  cellular  air-sacs.  The  lungs 
are  fundamentally  comparable  with  the  air-bladder  or  swim- 
ming bladder.  It  is  generally  situated  below  the  back-bone, 
and  is  developed  originally  as  an  offshoot  of  the  oesophagus. 
It  is  either  free,  not  connected  with  the  digestive  tract,  or  its 
original  attachment  may  be  retained  in  the  form  of  the 
"pneumatic  duct,"  which,  when  persistent,  opens  into  the 
oesophagus.  In  the  sharks  it  is  either  absent  or  exists  in  a 
rudimentary  state. 

The  kidneys  are  two  voluminous,  dark-red  lobulatecl  or- 
gans, lying  close  together  next  to  the  back-bone,  behind,  i.  c., 
above  the  air-bladder,  and  occupying  nearly  the  whole  length 
of  the  abdominal  cavity.  The  efferent  ducts  (ureters)  either 
pass  along  in  front  of  or  by  the  side  of  the  kidney,  and  some- 
times unite  to  form  a  single  sac,  the  outlet  of  which  is  situ- 
ated either  behind  or  below  the  generative  orifice.  It  has 
been  found  that  the  minute  structure  of  the  kidneys  of  em- 
bryo sharks  resembles  somewhat  the  segmental  organs  of 
worms,  the  original  kidney  being  composed  of  bundles  of 
ciliated  funnels,  like  those  of  worms,  combined,  however, 
with  Malpighian  bodies  and  renal  lobules  which  do  not  exist 
in  worms,  while  all  these  parts  have  a  common  duct,  the 
ureter,  which  also  does  not  exist  in  worms,  being  character- 
istic of  Vertebrates. 

In  the  fishes  the  sexes  are,  with  a  very  few  exceptions,  dis- 


414  ZOOLOGY. 

tinct.  The  ovaries  are  large  bodies,  either  discharging  the 
eggs  directly,  as  in  the  eel,  salmon,  and  trout,  into  the  body- 
cavity,  thence  passing  along  a  fold  of  the  peritoneum  ou4  of 
a  minute  opening  situated  directly  behind  the  venf/ t5r/*as  in 
most  bony  fishes,  there  is  a  duct  leading  from  each  ovary  to 
the  common  outlet.  In  the  sharks  and  skates  (Elasmo- 
branchs)  the  ovary  is  single,  and  the  oviducts  unite  behind 
to  serve  as  a  uterus  in  such  sharks  as  are  viviparous  ;  or  the 
same  parts  secrete  a  shell  in  the  egg-laying  sharks  (Scyllium) 
and  skates. 

The  reproductive  glands  of  most  fishes  are,  except  in  the 
breeding  season,  so  much  alike,  that  it  is  difficult  to  distin- 
guish them  except  by  a  microscopic  examination.  In  the 
breeding  season  the  ovaries  of  the  cod,  perch,  and  smelt  are 
very  large  and  yellowish,  while  the  testes  are  small  and  white. 
Fishes,  like  some  Amphibians  and  many  invertebrates,  may 
be  able  to  perform  the  reproductive  functions  before  they  are 
fully  mature  ;  in  fact,  some  fishes  continue  to  grow  as  long 
as  they  live. 

The  fishes  are  not  a  homogeneous  or  "closed,"  i.  e.,  well- 
circumscribed,  type,  as  the  birds  and  mammals,  for  the  form 
of  the  body  is  liable  to  great  variation,  the  differences  be- 
tween the  subdivisions  or  orders,  families  and  genera  being 
much  greater  than  in  birds  and  mammals. 

The  class  is  divided  into  three  subclasses,  viz.  :  the  Elas- 
mobranchii  (sharks  and  rays),  the  Ganoidea  (sturgeons,  gar- 
pikes,  etc.),  and  the  Teleostei,  or  bony  fishes.  The  classifi- 
cation we  adopt  is  that  of  Professor  Gill. 

Subclass  1.  Elasmobranchii  (Selachians,  or  Sharks  and 
Rays). — These  are  the  most  generalized  as  well  as  among  the 
oldest  of  all  fishes.  In  some  respects  they  stand  above  the  bony 
fishes,  with  some  features  anticipating  the  Amphibians,  while 
in  their  cartilaginous  skeleton,  their  numerous  gill-openings, 
and  their  general  appearance  they  are  scarcely  higher  than  the 
embryos  of  the  bony  fishes.  It  would  seem  as  if  a  shark  were 
an  embryo  fish,  which  had  been  hurried  by  nature  into  exist- 
ence with  some  parts  more  perfect  than  others,  in  order  to 
serve  in  the  Upper  Silurian  and  Devonian  times  as  destructive 


SHARKS  AND  RAYS.  415 

agents  to  the  types  of  invertebrate  life  which  then  became 
extinct,  partly  through  their  means.  These  and  ganoid  fishes 
having  thus  accomplished  their  work  were  replaced  in  the 
later  ages  by  more  highly  elaborated  and  specialized  forms, 
i.e.,  the  bony  fishes.  Sharks  and  skates  are  engines  of  de- 
struction, having  been  since  their  early  appearance  in  the 
Upper  Silurian  age  the  terror  of  the  seas.  Their  entire 
structure  is  such  as  to  enable  them  to  seize,  crush,  tear,  and 
rapidly  digest  large  invertebrates,  and  the  larger  marine 
members  of  their  own  class.  Hence  their  own  forms  are 
gigantic,  soft,  not  protected  by  scales  or  armor,  as  they  have 
in  the  adult  form  few  enemies.  Hence  they  do  not  need  a 
high  degree  of  intelligence,  nor  special  means  of  defence  or 
protection,  though  from  their  activity  the  circulatory  system 
is  highly  developed. 

In  the  general  form  the  sharks  are  long  and  somewhat  cylin- 
drical, with  the  head  rather  large,  often  pointed,  sometimes, 
in  in  the  hammer-headed  shark,  extraordinarily  broad,  with  a 
capacious  mouth,  situated  in  the  under-side  of  the  head. 
The  body  tapers  behind,  and  the  caudal  portion  is  unequally 
lobed,  the  upper  lobe  being  much  longer  than  the  lower, 
upturned  and  supported  by  a  continuation  of  the  vertebral 
column,  while  the  tail-fins  of  bony  fishes  are  equally  lobed 
and  consequently  called  homocercal ;  those  of  sharks  are 
unequally  lobed,  and  are  therefore  said  to  be  lieterocercal.  In 
this  respect  they  resemble  an  early  stage  in  the  development 
of  bony  fishes,  such  as  the  trout  or  herring.  Sharks,  like 
bony  fishes,  have  two  pectoral  and  generally  two  ventral 
fins  ;  these  two  pairs  of  fins  corresponding  to  or  homologous 
with  the  limbs  of  air-breathing  Vertebrates,  and  besides  this 
there  is  one  or  usually  two  dorsal  fins,  and  an  anal  fin,  the 
latter  situated  behind  the  vent. 

The  skin  is  either  smooth  or  covered  with  minute  placoid 
scales  (see  Fig.  385)  ;  the  integument  of  such  species  as 
are  provided  with  these  fine  scales  forming  shagreen.  While 
the  spinal  column  is  in  the  sharks  usually  cartilaginous,  and 
easily  cut  with  a  knife,  there  are  different  grades  of  devel- 
opment from  certain  forms,  as  the  Chimaera,  to  a  well-marked 


416  ZOOLOGY. 

column  or  series  of  biconcave  vertebrae,  with  the  cartilage  in 
part  replaced  by  bone,  forming  radiating  leaves  or  plates ; 
while  in  the  rays  or  skates  the  anterior  part  of  the  column 
is  bony. 

The  ribs  are  small,  sometimes  rudimentary.  The  skull  is 
rudimentary,  without  membrane-bones,  embryonic  in  char- 
acter, forming  a  simple  cartilaginous  brain-box,  without  pre- 
maxillary  or  maxillary  bones,  the  constitution  of  the  jaws  be- 
ing quite  unlike  that  of  the  bony  fishes,  the  jaws  being  formed 
of  elements,  i.  e.,  "cartilaginous  representatives  of  the  pri- 
mary palatoquadrate  arch  and  of  Meckel's  cartilage."  (Hux- 

ley.) 

There  arc  no  opercular  bones  such  as  cover  the  gill-open- 
ings in  bony  fishes,  their  place  being  taken  by  cartilaginous 
filaments. 

The  mouth  is  armed  in  most  sharks  with  numerous  sharp, 
flattened,  conical  teeth,  arranged  in  transverse  rows  and 
pointing  backwards  ;  they  are  never  fixed  in  sockets,  but 
imbedded  in  the  mucous  membrane  of  the  upper  and  under 
jaws.  In  the  Heterodontidae,  represented  by  Cestracion  or 
Port  Jackson  shark,  the  teeth  are  much  blunter  than  in 
other  living  sharks,  the  middle  and  hinder  teeth  having 
broad,  flattened  crowns,  forming  a  pavement  of  rounded 
teeth.  The  Devonian  sharks  were  in  most  cases  like  the 
Cestracion  in  this  respect.  In  the  Carboniferous  age,  sharks 
with  teeth  more  like  those  of  modern  forms  came  into  ex- 
istence ;  and  they  must  have  been  of  a  more  active  nature, 
the  sharp  teeth  directed  backwaixl  indicating  the  rapacity  of 
these  monsters,  which  darting  after  and  seizing  their  prey 
were  enabled  to  retain  it  by  the  backward-pointed  teeth  ; 
while  the  more  sluggish  Devonian  Cestracions  kept  near  the 
bottom  and  devoured  the  shelled  mollusks,  etc.,  possibly  Or- 
thoceratites,  Nautili,  and  Trilobites,  which  became  nearly 
extinct  about  the  time  the  type  of  pavement-toothed  sharks 
culminated. 

The  teeth  of  the  skates  or  rays  have  obtuse  points.  In 
Myliobatis  the  teeth  are  flattened  and  united  to  form  a  solid 
pavement,  so  that  the  mouths  of  these  large  rays  are  fur- 


DEVELOPMENT  OF  SHARKS  AND  RATS.         417 

nished  with  an  upper  and  nether  millstone  for  crushing  and 
comminuting  the  thick,  solid  shells  of  mollusks.  The  mouth 
in  both  sharks  and  rays  is  always  situated  on  the  underside 
of  the  head,  all  being  ground-feeders.  Such  sharks  as  rise 
to  the  surface  for  food  seize  it  by  turning  over  before  closing 
their  jaws  on  the  luckless  victim. 

The  throat  or  oesophagus  is  wide  ;  the  stomach  a  capacious 
sac,  and  the  intestine  short,  separated  from  the  stomach  by 
a  pyloric  valve.  The  spiral  valve  of  the  intestine  is  a  fold 
projecting  into  the  cavity  of  the  gut,  the  fixed  edge  forming 
a  spiral  line  around  the  inner  Avail  of  the  intestine. 

The  heart  consists  of  a  ventricle  and  auricle,  with  an 
aortic  bulb  which  pulsates  as  regularly  as  the  heart ;  and  the 
blood  must  be  sent  forward  with  great  force,  as  the  very  mus- 
cular bulb  is  provided  within  with  three  rows  of  semi-lunar 
valves. 

The  gills  are  pouch-like,  generally  five,  rarely  six  or  seven, 
in  number,  the  external  openings  or  gill-slits  being  usually 
of  moderate  size,  but  sometimes  long  and  large,  as  in  the 
basking  shark.  While  the  clefts  open  on  the  side  of  the 
neck  in  sharks,  in  the  skates  they  are  placed  beneath  the  neck. 

A  spiracle  or  opening  leads,  in  some  sharks,  from  the  up- 
per side  of  the  head  into  the  mouth.  According  to  Wyman 
this  is  the  remnant  of  the  first  visceral  cleft  of  the  embryo. 

In  the  brain  the  optic  thalami  are  separate  from  the  optic 
lobes,  the  olfactory  lobes  being  large  and  long  in  the  skates 
and  some  sharks.  The  medulla  forms  the  larger  part  of  the 
brain.  The  optic  nerves  unite,  as  in  higher  Vertebrates,  form- 
ing a  common  stem  or  cJiiasma,  before  diverging  to  the  eyes. 

The  eyes  of  some  sharks  have  a  third  lid  or  nictitating 
membrane  analogous  to  that  of  birds.  The  ear,  except  in 
Chimcera,  has  the  labyrinth  completely  surrounded  by  carti- 
lage. There  are  two  testes,  and  usually  two  ovaries,  but  in 
the  dog-fishes  and  the  nictitating  sharks  there  is  but  a  single 
ovary.  The  oviducts  are  true  "Fallopian  tubes,"  expanding 
posteriorly  into  uterine  chambers,  which  unite  and  open 
into  the  cloaca.  (Huxley.) 

The  sharks  and  skates  are  not  prolific ;  having  but  few 


418  ZOOLOGY. 

enemies  they  do  not  lose  much  ground  in  the  struggle  for 
life.  The  oviparous  forms  such  as  certain  sharks,  skates, 
and  Chimcera,  lay  large  eggs  enclosed  in  tough,  leathery, 
purse-shaped  cases.  The  other  Elasmobranchiates  are  vivip- 
arous, bringing  forth  their  young  alive.  In  Mustelus  and 
CarcJiarias  a  rudimentary  "  placenta"  analogous  to  that  of 
Mammals  is  developed  from  the  yolk.  The  following  ac- 
count of  the  development  of  the  dog-fish  (Mustelus),  which 
is  condensed  from  Balfour,  may  be  found  to  be  applicable  to 
sharks  in  general : 

The  blastoderm  or  germinal  disk  is  a  large  round  spot 
darker  than  the  rest  of  the  yolk,  bordered  by  a  dark  line 
(really  a  shallow  groove).  Segmentation  occurs  much  as  de- 
scribed in  the  bony  fishes,  reptiles,  and  birds.  The  upper 
germ-layer  (epiblast)  arises  much  as  in  the  bony  fishes,  the 
Batrachians  and  birds,  while  the  two  inner  germ-layers  are 
not  clearly  indicated  until  a  considerably  later  stage.  The 
segmentation-cavity  is  formed  nearly  as  in  the  bony  fishes. 
There  is  no  invagination  of  the  outer  germ-layer  to  form  the 
primitive  digestive  cavity,  as  in  Amphioxus,  the  lamprey, 
sturgeons,  and  Batrachians,  but  the  Selachians  agree  with 
the  bony  fishes,  the  reptiles,  and  birds,  in  having  the  alimen- 
tary canal  formed  by  an  infolding  of  the  innermost  germ- 
layer,  the  digestive  track  remaining  in  communication  with 
the  yolk  for  the  greater  part  of  embryonic  life  by  an 
umbilical  canal.  This  mode  of  origin  of  the  digestive  cav- 
ity, Balfour  regards  as  secondary  and  adaptive,  no  "gas- 
trula"  (Haeckel)  being  formed  as  in  Amphioxus,  etc.  The 
embryo  now  rises  up  as  a  distinct  body  from  the  blastoderm, 
just  as  in  other  Vertebrates,  and  there  is  a  medullary  groove 
along  the  middle  line,  and  by  the  time  this  has  appeared  the 
middle  and  inner  germ-layers  are  clearly  indicated.  After 
this  development  continues  in  much  the  same  manner  as  in 
the  chick. 

At  this  time  the  embryo  dog-fish  externally  resembles  the 
trout ;  the  chief  difference  is  an  internal  one,  the  outer 
germ-layer  not  being  divided  into  a  nervous  and  epidermal 
sublayer  as  in  the  bony  fishes. 


DEVELOPMENT  OF  SHARKS  AND  RAYS.         419 

The  next  external  change  is  the  division  of  the  tail-end 
into  two  caudal  lobes.  The  notochord  arises  as  a  rod-like 
thickening  of  the  third  germ-layer,  from  which  it  afterwards 
entirely  separates,  so  that  the  germ,  if  cut  transversely, 
would  appear  somewhat  as  in  the  embryo  bird. 

The  primitive  vertebrae  next  arise,  and  about  this  time  the 
throat  becomes  a  closed  tube.  The  head  is  now  formed  by 
a  singular  flattening-out  of  the  germ,  like  a  spatula,  while 
the  medullary  groove  is  at  first  entirely  absent.  The  brain 
then  forms,  with  its  three  divisions,  into  a  fore,  middle,  and 
hind  brain.  Soon  about  twenty  primitive  vertebrae  arise, 
and  by  this  time  the  embryo  is  very  similar,  in  external 
form,  to  any  other  vertebrate  embryo,  and  finally  hatches  in 
the  form  of  the  adult. 

The  skate  was  found  by  Wyman  to  be  at  first  long  and 
narrow,  the  dorsal  and  anal  fins  extending  to  the  end  of  the 
tail,  as  in  the  eel.  Soon  after  it  becomes  shark-shaped,  and 
finally  assumes  the  skate  form.  Thus  skates  pass  through 
a  shark-stage,  and  this  accords  with  the  position  in  nature 
of  skates,  since  they  are,  as  a  whole,  a  more  specialized  as 
well  as  more  modern  group  than  the  sharks.  Wyman  found 
that  there  are  in  the  skate  at  first  seven  branchial  fissures, 
the  most  anterior  of  which  is  converted  into  the  spiracle, 
which  is  the  homologue  of  the  Eustachian  tube  and  the 
outer  ear-canal ;  the  seventh  is  wholly  closed  up,  no  trace  re- 
maining, while  the  five  others  remain  permanently  open. 

The  Elasmobranchs  are  subdivided  into  two  orders  (re- 
garded by  Gill  as  super-orders,  the  Plagiostomi,  represented 
by  the  sharks  and  rays,  and  the  Holocephali,  the  type  of 
which  is  Cliimcera. 

Order  1.  Plagiostomi. — In  the  sharks  and  skates  the  teeth 
are  very  numerous  ;  the  gill-slits  are  uncovered.  The  rays 
or  skates  differ  from  the  sharks  in  their  broad,  flat  bodies, 
with  the  gill-slits  opening  below ;  the  great  breadth  of  the 
body  is  due  to  the  enlargement  of  the  pectoral  fins  which 
are  connected  by  cartilages  to  the  skull ;  there  is  likewise  no 
median  articular  facet  upon  the  occiput  or  base  of  the 
skull,  for  the  first  vertebra. 

The  most  common  of  our  Selachians  is  the  mackerel  shark 


420  ZOOLOGY. 

or  Isurus  punctatus  (Fig.  389).  The  head  is  conical,  with 
the  nostrils  under  the  base,  and  the  lobes  of  the  tail  are 
nearly  equal.  It  is  from  four  to  eight  feet  in  length,  and  is 
often  taken  in  fish-nets,  being  a  surface-swimmer.  In  the 
thresher  shark  (Alopecias  vulpes  Cuvier),  the  upper  lobe  of 
the  tail  is  nearly  as  long  as  the  body  of  the  shark  itself.  It 
grows  twelve  or  fifteen  feet  in  length,  and  lives  on  the  high 
seas  of  the  Atlantic. 

Nearly  twice  the  size  of  the  thresher  is  the  great  basking 
shark,  Selache  (Cetorhinus)  maxima  Cuvier,  of  the  North 
Atlantic,  which  becomes  nine  to  thirteen  metres  (thirty  or 
forty  feet)  in  length.  It  has  very  large  gill-slits,  and  is  by 
no  means  as  ferocious  as  most  sharks,  since  it  lives  on  small 


Fig.  389.— Mackerel  Shark.— From  Tenney's  "Zoology." 

fishes,  and  in  part,  probably,  on  small  floating  animals,  strain- 
ing them  into  its  throat  through  a  series  of  rays  or  fringes  of 
an  elastic,  hard  substance,  but  brittle  when  bent  too  much, 
and  arranged  like  a  comb  along  the  gill-openings,  the  teeth 
being  very  small. 

Among  tne  smaller  sharks  is  the  dog-fish  (Squalus  Ameri- 
canus  Storer),  distinguished  by  the  sharp  spine  in  front  of 
each  of  the  two  "dorsal  fins.  It  is  caught  in  great  numbers 
for  the  oil  which  is  extracted  from  its  liver.  The  dog-shark 
(Mustelus  canis  Dekay),  which  is  a  little  larger  than  the 
dog-fish,  becoming  over  a  metre  (four  feet)  long,  brings  forth 
its  young  alive.  In  the  European  Mustelus  Icevis  Risso  a 
so-called  placenta  is  developed,  while  it  is  wanting  in  the 
Mustelus  vulgaris  of  Miiller  and  Henle. 


SHARKS  AND  RATS.  421 

Among  the  more  aberrant  sharks  is  the  hammer-headed 
Sphyrna  zygcena  (Linn.),  which  grows  to  the  length  of  twelve 
feet,  and  is  one  of  the  most  rapacious  and  formidable  of  the 
order. 

Of  the  rays  and  skates,  the  saw-fish  approximates  most 
to  the  sharks.  Its  snout  is  prolonged  into  a  long,  flat 
bony  blade,  armed  on  each  side  with 
large  teeth.  Pristis  antiquorum 
Latham  (Fig.  390),  the  common  saw- 
fish, inhabits  the  Mediterranean  Sea 
and  the  Gulf  of  Mexico  ;  it  is  vivipa- 
rous (Cat  on.)  Pristis  Perroteli  lives 
in  the  Senegal  River,  while  Carclmrias 
yanyeticus  is  found  sixty  leagues  from 
the  sea. 

The  genuine  skates  or  rays  have  the 
body  broad  and  flat,  rhomboidal  (ow- 
ing to  the  great  extension  of  the 
thick  pectoral  fins).  Portions  of  the 
ventral  fins  in  the  males  are  so  elon- 
gated and  modified  as  to  form  intro- 
mittent  and  clasping  organs.  They 
swim  close  to  the  bottom,  feeding  upon 
shell-fish,  crabs,  etc.,  crushing  them 
with  their  powerful  flattened  teeth. 
The  spiracle  is  especially  developed  in 
the  rays,  while,  as  observed  by  Gar- 
man,  in  the  majority  of  the  sharks 
which  swim  in  midwater  or  near  the 
surfac3,  the  water  enters  the  mouth 
and  passes  freely  out  of  the  gill-open- 
ings, but  in  the  rays,  which  remain  at 

,!  Fig.  390.—  Beak  of  Saw-fish, 

the  bottom,  the  purer  sea-water  enters  seen  from  below,  showing  its 
the  spiracle  from  above  to  pass  out  of  ^ 


the  gill-slits. 

The  smallest  and  most  common  skate  of  our  northeast- 
ern Atlantic  coast  is  Raja  erinacea  Mitchell.  It  is  one  half 
of  a  metre  (twenty  inches)  in  length,  and  the  males  are 
smaller  than  the  females.  The  largest  species  is  the  barn- 
door skate,  Raja  Icevis  Mitchell,  which  is  over  a  metre  (forty- 


422 


ZOOLOGY. 


two  inches)  long.  Raja  eglanteria  Lacepede  (Fig.  391) 
ranges  from  Cape  Cod  to  the  Caribbean  Sea.  The  smaller 
figures  in  Fig.  391  represent  respectively  the  mouth  and 
gill-slits,  and  the  jaws  of  Myliobatis  fremenvillii  Lesueur. 

In  the  torpedo  the  body  is  somewhat  oval  and  rounded. 
Fig.  392  represents  Torpedo  marmoratus,  of  the  Mediter- 
ranean Sea. 

Our   native   species,   found   mostly  in  winter,   especially 

on  the  low  sandy 
shores  of  Cape  Cod, 
is  Torpedo  occiden- 
talis  Storer.  Its  bat- 
teries and  nerves  are 
substantially  as  in 
the  European  spe- 
cies. The  electrical 
organs  are  construct- 
ed on  the  principle 
of  a  Voltaic  pile, 
consisting  of  two 
series  or  layers  of 
hexagonal  cells,  the 
space  between  the 
numerous  fine  trans- 
verse plates  in  the 
cells  filled  with  a 
trembling  jelly-like 
mass,  each  cell 
representing,  so  to 

Fig.  391.— Raja  eglanteria,  male.    Mouth  and  gill-    SPCak,  a  Levden  iai* 
slits,  jaws  and  teeth  of  Myliobatis  fremenvillii  ? .  *  J,        ,  J      * 

There  are  about  470 

cells  in  each  battery,  each  provided  with  nerves  sent  off  from 
the  fifth  and  eighth  pairs  of  nerves.  The  dorsal  side  of 
the  apparatus  is  positively  electrical,  the  ventral  side  nega- 
tively so.  The  electrical  current  passes  from  the  dorsal  to 
the  ventral  side.  When  the  electrical  ray  is  disturbed  by  the 
touch  of  any  object,  the  impression  is  conveyed  by  the  sen- 
sory nerves  to  the  brain,  exciting  there  an  act  of  the  will 
which  is  conveyed  along  the  electric  nerves  to  the  batteries, 


THE  ELECTRICAL  RAY. 


423 


producing  a  shock.  The  benumbing  power  is  lost  by  fre- 
quent exercise,  being  regained  by  rest ;  it  is  also  increased 
by  energetic  circulation  and  respiration.  As  in  muscular 


Fig.  392.—  Torpedo  marmoratus.  a,  cerebrum:  &,  the  medulla ;  c,  spinal  cord  ; 
d  and  &',  electric  portion  of  the  trigeminate  or  fifth  pair  of  nerves  ;  ee\  electric  portion 
of  the  pneumogastric  or  eighth  pair  of  nerves  ;  /,  recurrent  nerve  ;  g,  left  electric 
organ  entire  ;  g1 ',  right  electric  organ  dissected  to  show  the  distribution  of  the  nerves  ; 
h,  the  last  of  the  hrauchial  chambers  ;  i,  mucus-secreting  tubes. — From  Gervais  and 
Van  Beneden. 


exertion  the  electrical  power  is  increased  by  the  action  of 
strychnine  (Owen). 

Marey  has  more  recently  made  interesting  experiments  on 
the  torpedo,  examining  the  discharge  of  this  fish  with  the 


424  ZOOLOGY. 

telephone.  Slight  excitations  provoked  a  short  croaking 
sound.  Each  of  the  small  discharges  was  composed  of  a 
dozen  fluxes  and  pulsations,  lasting  about  one  fifteenth  of  a 
second.  The  sound  got  from  a  prolonged  discharge,  how- 
ever, continued  three  to  four  seconds,  and  consisted  of  a  sort 
of  groan,  with  tonality  of  about  mi  (165  vibrations),  agree- 
ing pretty  closely  with  the  result  of  graphic  experiments. 

Marey  has  also  studied  the  resemblance  of  the  electrical 
apparatus  of  the  electrical  ray  or  torpedo  and  a  muscle. 
Both  are  subject  to  will,  provided  with  nerves  of  centrifugal 
action,  have  a  very  similar  chemical  composition,  and  re- 
semble each  other  in  some  points  of  structure.  A  muscle  in 
contraction  and  in  tetanus  executes  a  number  of  successive 
small  movements  or  shocks,  and  a  like  complexity  has  been 
proved  by  M.  Marey  in  the  discharge  of  the  torpedo. 

The  sting-rays  (Trygori)  have  no  caudal  fin,  but  the  spinal 
column  is  greatly  elongated,  very  slender,  and  armed  with  a 
long,  erect  spine  or  "sting."  Some  live  in  fresh  water; 
several  species  of  sting-rays  (Potamotrygon)  inhabit  the  large 
rivers  of  Brazil  and  Surinam,  as  the  Amazon,  Tapajos,  Ma- 
deira, and  Araguay,  digging  holes  in  the  sand,  in  which  they 
lie  flat  and  await  their  prey.  In  this  connection  it  may  be 
said  that  Raia  fluviatilis  of  India  has  been  taken  near  Ram- 
pur,  nearly  1000  miles  above  tide-reach. 

Myliobatis  has  the  teeth  forming  a  solid  plate  or  pavement. 
The  devil-fish  (Ceplialopierus  diabolus  Mitchell)  of  the  coast 
of  South  Carolina  and  Florida  is  the  largest  of  our  rays,  be- 
ing eighteen  feet  across  from  tip  to  tip  of  its  pectoral  fins, 
and  ten  feet  in  length,  weighing  several  tons.  It  sometimes 
seizes  the  anchors  of  small  vessels  by  means  of  the  curved 
processes  of  its  head  and  swims  rapidly  out  to  sea,  carrying 
the  craft  along  with  it. 

Order  2.  Holocephati.—This  small  but  interesting  group 
is  represented  by  CMmcera  of  the  north  Atlantic,  and  Cal- 
lorliynchus  of  the  antarctic  seas.  In  these  fishes  the  four 
gill-openings  are  covered  by  an  opercular  membrane  ;  thus 
approaching  the  true  bony  fishes,  and  there  are  but  four  teeth 
in  the  upper  and  two  in  the  lower  jaw.  The  brain  of  Chi- 
maera  is  said  by  Wilder  to  combine  characters  of  those  of 


GANOID  FISHES.  425 

Selachians,   Ganoids,  and  Batrachians.     Chimcera  plumbea 
Gill  lives  in  deep  water  off  the  coast  of  New  England. 

Subclass  2.  G-anoidei  (Gar pikes,  Lung  -  Fishes). — The 
term  Ganoid  was  applied  to  these  fishes  from  the  form  of 
the  scales,  which  in  most  of  the  species  are  angular,  square, 
or  rhomboidal  and  covered  with  enamel,  as  seen  in  the  com- 
mon garpike.  In  others,  however,  as  in  the  Ami  a  and  Dip- 
noans,  the  scales  are  rounded  or  cycloid.  These  fish,  i.e., 
both  the  genuine  Ganoids  and  Dipnoi,  were  the  character- 
istic fishes  of  the  Devonian  age,  which  has  consequently  been 
called  the  Age  of  Fishes,  there  being  no  bony  fishes  (Teleos- 
tei)  at  that  time.  The  forms  Avere  much  larger  than  at 
present,  far  more  numerous  in  species,  genera,  and  families, 
and  they,  with  the  sharks,  were  the  rulers  of  the  sea. 

At  the  present  day  the  type  is  nearly  extinct,  being  repre- 
sented by  such  isolated  forms  as  the  sturgeon,  the  paddle- 
fish,  the  lung-fish  (Dipnoi),  the  garpikes,  and  the  American 
mud-fish  (Amid).  Like  most  of  the  palaeozoic  types  of  life, 
the  Ganoids  were  both  generalized  forms  and  also  combined 
the  characters  of  classes  of  animals  not  then  in  existence  ;  in 
other  words  they  were  synthetic  or  comprehensive  types. 
Thus  in  forms  like  Amia,  the  Teleostean  fishes  were  antici- 
pated ;  in  the  Dipnoi,  with  their  external  gills  and  lungs, 
not  only  the  Amphibians,  but  even  the  reptiles  were  indica- 
ted in  their  hearts  with  two  auricles,  just  as  the  Trilobites  and 
Merostomata,  as  indicated  by  the  structure  of  the  living 
king-crab,  combined  with  the  structure  of  Crustaceans,  fea- 
tures which  became  in  a  degree  reproduced  in  the  terrestrial 
scorpions  and  spiders  which  subsequently  appeared.  Owing 
to  this  intermixture  of  ancient  and  modern  characteristics, 
this  reaching  up  and  out  of  the  piscine  type  of  life  over  into 
the  amphibian  and  reptilian  boundaries,  the  classification, 
i.  e.,  actual  position  in  nature  of  the  Ganoids,  becomes  very 
difficult,  and  the  views  of  naturalists  regarding  their  system- 
atic position  are  very  discordant.  If,  as  insisted  on  by  Gill, 
we  recognize  the  fact  that  the  Ganoids  are  an  older,  more 
generalized,  and  therefore  more  elementary  group,  and  the 
osseous  fishes  a  newer,  more  highly  specialized  group,  and 


426  ZOOLOGY. 

that  there  is  a  natural  series  of  forms  leading  from  the  stur- 
geon, which  is  nearest  the  Elasmobranchs,  up  through  the 
Dipnoans  to  the  true  Ganoids,  and  that  the  latter,  through 
Amia,  leads  to  the  bony  fishes,  we  shall  have  a  clue  to  the 
intricate  relations  existing  between  them  and  the  other  sub- 
classes of  fishes.* 

The  Ganoids  of  the  present  day  are  well  nigh  confined  to 
fresh  water,  the  sturgeons  alone  living  in  the  sea  as  well  as 
ascending  rivers ;  though  the  Devonian  and  carboniferous 
forms  occur  as  marine  fossils. 

In  synthetic  forms,  like  the  Ganoids,  it  is  difficult  to  find 
absolute  characters  separating  them  from  the  Elasmobranchs 
on  the  one  hand  and  the  Teleosts  on  the  other.  The  diag- 
nostic characters  are  the  following  :  the  skeleton  is  either 
wholly  cartilaginous,  or  partly  or  wholly  bony  ;  the  skin  is 
either  smooth,  or  with  cycloid,  or  usually  with  ganoid  scales  ; 
the  gills  are  free  ;  the  gill-opening  is  covered  with  an  oper- 
cular  bone  ;  the  first  fin-rays  generally  sharp  ;  the  air-blad- 
der with  a  pneumatic  duct ;  the  embryos  sometimes  with  ex- 
ternal gills. 

The  spinal  column  is  usually  cartilaginous ;  in  the  Dip- 
noans, the  sturgeons,  the  paddle-fish  and  allies,  the  notochord, 
with  its  sheath,  is  persistent ;  while  in  Polypterus  and  Amia 
the  spinal  column  is  completely  bony,  the  vertebrae  being 
amphicoslous,  i.  e., biconcave  ;  while  in  the  garpike  (Lepidos- 
teus)  the  vertebras  are  convex  in  front  and  concave  behind. 
The  cartilaginous  skull  is  covered  by  broad,  thin  membrane- 
bones,  as  seen  in  the  sturgeon.  The  tail  is  heterocercal,  the 
lobes  being,  in  Amia,  nearly  equal. 

The  brain  is  as  in  the  bony  fishes,  but  the  optic  nerves 
unite  in  a  chiasma.  The  heart  and  aortic  bulb  are  as  in  the 
Elasmobranchs,  and  all  but  Lepidosteus  have  a  well-devel- 
oped spiral  valve  in  the  intestine,  the  valve  being  rudimentary 

*  Although  strongly  inclined  to  regard  the  Dipnoans  from  their  am- 
phibian and  reptilian  characters  as  types  of  a  subclass,  Dipnoi,  yet  in 
deference  to  the  principles  stated  by  Gill,  which  we  had  previously  fol- 
lowed independently  in  the  classification  of  the  neocaridan  and  palseo- 
caridan  Crustacea,  we  here  adopt  the  classification  of  Prof.  Gill. 


DEVELOPMENT  OF  THE  STURGEON.  427 

in  the  garpikes.  The  oviducts  communicate  with  the  ure- 
ters as  in  the  sharks  and  amphibians.  The  different  modifi- 
cations of  Ganoid  structure  may  be  observed  in  the  examples 
of  the  different  orders. 

Many  of  the  Ganoids  of  the  Upper  Silurian  and  Devonian 
rocks  belonged  to  the  groups  CeplicJlaspidce  and  Placoder- 
mata.  In  the  Cephalaspids,  represented  by  the  singular 
Cephalaspis  Lyellii  of  Agassiz,  the  broad  head  was  covered 
by  a  single  semi-circular  plate,  with  large  orbits  above,  the 
mouth  being  below.  The  pectoral  fins  were  rayless  folds  of 
the  skin  ;  the  body  behind  the  head  was  covered  with  rhom- 
boidal  scales,  and  provided  with  a  dorsal  fin.  The  Pteraspis 
had  a  head-shield  composed  of  seven  pieces.  Among  the 
Placoderms,  Ptericlithys  had  a  plated  head  half  as  long  as 
the  body,  the  tail  short  and  scaled.  These  fishes,  the  earliest 
known  Vertebrates,  were  bottom-feeders.  Nothing  is  known 
as  to  the  nature  of  their  jaws  or  teeth. 

Order  1.  Chondroganoidei. — In  these  Ganoids  the  dorsal 
chord  is  not  ossified ;  the  skull  is  cartilaginous,  covered  with 
membrane-bones  ;  they  are  either  toothless  or  with  small 
teeth.  The  skin  is  naked  as  in  the  paddle-fish,  or  protected 
as  in  the  sturgeons  with  very  large,  bony,  solid  plates.  The 
sturgeons  have  the  snout  long  and  pointed,  with  the  mouth 
underneath,  and  toothless.  Acipenser  sturio  Linn,  is  the 
common  sea-sturgeon  of  our  coast,  ascending  rivers.  The 
shovel-nosed  sturgeon,  Scapliirhynchops  platyrhynchus  has  a 
spade-like  snout.  It  inhabits  the  waters  of  the  Mississippi 
Valley.  Salensky  has  studied  the  embryology  of  the  Russian 
sturgeon.  The  freshly-laid  eggs  are  two  millimetres  in  di- 
ameter, the  yolk  undergoes  nearly  total  segmentation,  thus 
connecting  most  Vertebrates  in  which  the  eggs  only  partially 
segment,  with  the  Amphioxus,  lampreys,  and  amphibia,  in 
which  segmentation  is  total.  The  skeleton  is  developed 
much  as  in  the  Elasmobranchs.  The  sheath  of  the  noto- 
chord  develops  in  three  weeks  after  hatching.  At  the 
end  of  the  third  week  the  upper  and  lower  vertebral  arches 
appear,  arising  as  in  other  fishes.  The  skull  is  indicated  in 
two  or  three  weeks  after  hatching. 


428  ZOOLOGY. 

The  singular  spoon-bill,  Polyodon  folium  Lacepede,  is  five 
feet  long  ;  it  is  smooth-skinned  and  has  a  snout  one-third  as 
long  as  the  body,  and  spatulate,  with  thin  edges.  It  has  a 
very  wide  mouth  with  minute  teeth,  and  lives  on  small 
Crustacea.  It  abounds  in  the  Mississippi,  and  its  larger 
tributaries. 

Order  2.  Dipnoi. — The  lung  fishes  are  so  called  from  the 
fact  that  often  being  in  pools  and  streams  liable  to  dry  up, 
they  breathe  air  directly,  having  true  lungs,  like  those  of 
Amphibians,  as  well  as  gills.  From  the  nature  of  their  lungs 
and  heart,  the  Dipnoans  are  quite  different  from  all  other 
fishes,  anticipating  in  nature  the  coming  of  Amphibians, 
while  on  the  other  hand  the  notochord  and  sheath  is  persist- 
ent, and  as  they  were  characteristic  and  more  numerous  in 
Devonian  times,  they  may  be  said  to  be  a  prematurative 
type. 

The  body  of  the  Dipnoans  is  somewhat  eel-shaped,  though 
not  very  long  in  proportion  to  its  thickness,  and  is  covered 
with  cycloid  scales.  The  pectoral  and  ventral  fins  are  long, 
narrow,  and  pointed,  and  there  is  a  long  caudal  fin  which  is 
protocercal,  a  term  proposed  by  Wyman  to  designate  the  form 
of  the  caudal  fin  of  embryo  sharks.  In  fact,  the  tail  of  the 
young  garpike,  as  of  embryo  Teleosts  or  bony  fishes,  is  at 
first  protocercal,  afterwards  being  heterocercal  in  adult 
Ganoids,  such  as  the  garpike,  and  in  the  embryo  and 
early  free  stage  of  most  bony  fishes  ;  the  tail  in  the  latter 
becoming  finally  homocercal  or  equal-lobed.  Thus  the 
tail  of  the  Dipnoans  may  be  said  to  be  embryonic,  i.e., 
protocercal. 

The  spinal  column  is  represented  by  a  simple  notochord  and 
sheath  ;  within  the  latter  the  basal  ends  of  the  bony  neural 
arches  and  ribs,  and  near  the  tail  the  lower  (haemal)  arches 
are  imbedded.  The  skull  is  cartilaginous.  The  extremity  of 
the  lower  jaws  supports  large  tooth-like  plates  (dentary  plates) 
which  shut  in  between  the  few  palatine  teeth  ;  in  Ceratodus 
these  plates  are  single,  and  in  all  Dipnoans  these  single  den- 
tary plates  are  very  characteristic  of  the  group.  The  narrow 
pectoral  and  ventral  fins  are  supported  by  a  single,  median, 


LUX  a  FISHES. 


429 


many-jointed  cartilaginous  rod,  to  which  is  attached  fine  fin- 
rays,  supporting  the  thin  edge  of  the  fin. 

The  spiral  valve  and  cloaca  are  present  in  the  intestinal 
tract.  In  Polypterus  the  cerebral  hemispheres  are  larger 
than  the  olfactory  lobes,  and  there  is  an  optic  chiasma  ;  the 
heart  has  besides  the  right  large  auricle,  a  left  smaller  one 
which  receives  the  blood  from  the  lungs,  and  a  single  ven- 
tricle, as  in  Amphibians  and  most  reptiles ;  they  have  true 
nostrils.  The  lungs  are  like  those  of  Amphibians,  and  in 
addition  they  possess  both 
internal  and  external  gills 
(Fig.  393),  the  latter  nearly 
aborted  in  the  adult. 

The  genus  Ceratodus  was 
originally  named  by  Agassiz,    .  Fjs-  m— External  gills  of  a  young  PO- 

J  /       &         .       lypterus  bichir.    Jr,  external  gills. 

from  teeth  found  in  Jurassic 

and  Triassic  strata  in  Europe.  Living  specimens  were  found 
by  Mr.  Krefft  in  Queensland,  Australia,  and  called  Ceratodus 
Fosteri  Krefft  (Fig.  394).  This  fish  is  rather  more  elemen- 
tary in  form  than  Lepidosiren,  the  body  being  stouter,  and 
the  large  scales  of  the  body,  with  the  fin-like  paddles  and 
distinctly  rayed  vertical  fins,  cause  it  to  resemble  more  closely 
ordinary  bony  fishes  than  Lepidosireii  (Griinther).  Moreover 


Fig.  394.— Ceratodus,  or  Australian  Lung-Fish.  (The  tail  in  nature  ends  in  a  point.) 
—After  Giinther  ;  from  Nicholson. 

the  lung  is  single,  and  not  used  so  much  as  the  two  perfect 
lungs  of  Lepidosiren.  It  attains  a  length  of  six  feet.  It 
can  breathe  by  either  gills  or  lungs  alone.  When,  Gtinther 
thinks,  the  fish  is  compelled  to  live  during  droughts  in  thick 
muddy  water  charged  with  gases  which  are  the  product  of 
decomposing  organic  matter,  it  is  obliged  to  use  its  lungs. 
The  gills  are  more  like  those  of  ordinary  bony  fishes  than 
those  of  Lepidosiren.  It  lives  on  the  dead  leaves  of  aquatic 
etc.  The  local  English  name  is  "flat-head,"  the 


430 


ZOOLOGY. 


native  name  being  "  barramundi. "  Nothing  is  known  of  its 
breeding  habits  or  mode  of  development.  The  eggs  when 
ready  to  be  laid  are  2.5  millimetres  in  diameter.  The  lower 
part  of  the  oviduct  is  much  as  in  Menopoma.  Fossil  teeth 
of  Ceratodus  occur  in  the  Jurassic  beds  of  Wyoming,  and  two 
species  have  been  found  in  still  older  beds  in  Illinois,  regarded 
by  Cope  as  either  Upper  Carboniferous  or  Permian.  Thus, 


Pig.  395,—Protopterus  annectenn,  a  Lung-fish  of  Africa.    One  third  natural  size. 

as  remarked  by  Giinther,   we  have  in   Ceratodus  a  genus 
which  has  survived  from  the  Triassic  period. 

The  lung-fish  are  distinguished  by  two  well-formed  lungs, 
and  the  narrow  ribbon-like  fins.  In  Lepidosiren  paradoxa 
Fitzinger,  there  are  five  gill-arches,  with  four  slits,  and  the 
body  is  rather  longer,  more  eel-like,  with  a  blunter  snout 
than  in  Protopterus.  It  grows  to  one  metre  in  length,  and 


Fig.  396.— Skeleton  of  Proiopterus  annectens,  showing  the  protocercal  tail  and  the 
simple  rod-like  limbs,  the  pelvic  and  shoulder  girdles,  and  the  nature  of  the  jaws. 
ch,  notochord  ;  p,  bones  representing  the  haemal  arche*  attached  to  the  notochordal 
sheath  ;  hs,  haemal  spines  ;  in,  ih,  rays  of  the  caudal  fin.— After  Owen. 

inhabits  the  rivers  of  Brazil.  This  is  represented  in  Africa 
by  the  closely  allied  Protopterus  annectens  Owen  (Figs.  395 
and  396  skeleton),  which  has  six  gill-arches,  with  three 
pairs  of  external  gills  in  the  young.  It  is  40-70  centimetres 
in  length.  It  lives  on  leaves  in  the  White  Nile,  Quilimani, 
Niger,  Gambia,  and  their  tributaries.  It  buries  itself  in  the 
mud  a  foot  deep.  Gtinther  states  that  numerous  examples 


POLTPTBRU8. 


481 


of  Lepidosiren  "  have  been  kept  in  captivity,  but  none  have 
shown  a  tendency  to  leave  the  water." 

The  modern  Dipnoi  represent  the  Devonian  fishes  Holop- 
tychius,  Dipterus,  and  Phaneroplenron, 
and  the  American  Dinichthys  Torrelli 
of  the  Devonian  rocks  of  Ohio,  which 
is  said  by  Newberry  to  have  been  about 
five  metres  (from  fifteen  to  eighteen 
feet)  in  length,  and  a  metre  in  thickness, 
being  inferior  only  in  size  to  the  Aster '0- 
lepis,  a  Placoderm  of  the  old  red  sand- 
stone of  Great  Britain. 

Order  3.  Branchioganoidei. — Here  be- 
longs the  Polypterus  of  the  Nile  and 
Senegal.  In  these  Ganoids  the  tail  is 
either  protocercal  or  heterocercal ;  the 
scales  are  cycloid  or  rhomboid.  The 
dorsal  fin  is  long,  subdivided  into  divis- 
ions, each  with  a  separate  ray  and  spine. 
Polypterus  Ucliir  Geoffroy  (Fig.  397) 
has  a  protocercal  tail.  The  young  has 
external  gills  (Fig.  393).  It  inhabits  the 
river  Nile,  P.  senegalus  the  Senegal. 
Calamoichthys  differs  in  having  no  ven- 
tral fins  and  in  its  elongated  form.  It 
inhabits  the  rivers  of  Old  Calabar.  Al-  C%f\  \ 
lied  to  these  living  forms  are  the  De- 
vonian Osteolepis,  Ccelacanthus,  and  Ho- 
loptychius. 

Order  4.  Hyoganoidei. — This  group  is 
represented  by  the  garpike  and  Amia  or 
mud-fish  of  the  United   States,  which 
is    an   annectant  form   connecting   the 
Ganoids  with  the   Teleosts.      In   these     r.lg.w.         ^^^ 
fishes  the  spinal  column   is  bony,  the  chir.-From  cuvicr. 
tail  partially  heterocercal. 

In  Lepidosteus  (Fig.  398,  L.  osseus  Agassiz)  the  body  is 
long,  the  jaws  long  and  armed  with  sharp  teeth,  the  vertebrae 
are  opisthocoelous,  and  the  scales  are  large  and  rhomboidal, 


433  ZOOLOGY. 

while  the  air-bladder  is  cellular,  lung-like.  Fossil  species  oc- 
cur with  those  of  Amia  in  the  tertiary  rocks  of  the  West. 
Lepidosteus  osseus  Agassiz,  the  bony  gar,  with  a  long,  slender 
snout,  is  sometimes  five  feet  long  ;  L.  platystomus  Rafin. 
has  a  short  nose,  while  the  alligator  gar,  L.  spatula  Lace- 
pede,  has  a  short  and  wide  snout,  and  grows  to  a  larger  size 
(nearly  three  metres)  than  the  other  species,  and  inhabits 
the  Mississippi  Valley.  The  garpikes  are  carnivorous,  very 
rapacious,  and  are  said  to  destroy  large  numbers  of  food- 
fishes.  They  usually  remain  near  the  surface  of  the  water, 
emitting  bubbles  of  air  and  apparently  taking  in  a  fresh 
supply.  Wilder  has  observed  Amia  inhaling  air,  and  re- 
marks that  "so  far  as  the  experiments  go,  it  seems  probable 
that,  with  both  Amia  and  Lepidosteus,  there  occurs  an  inha- 
lation as  well  as  exhalation  of  air  at  pretty  regular  intervals, 
the  whole  process  resembling  that  of  the  Menobranchus  and 
other  salamanders,  and  the  tadpoles,  which,  as  the  gills 


Fig.  398.— Garpike.    From  Tenney's  Zoology. 

shrink  and  the  lungs  increase,  come  more  frequently  to  the 
surface  for  air."  Both  of  these  fishes  are  very  tenacious  of 
life  and  withstand  removal  from  water  much  better  than 
bony  fishes  and  sturgeons,  on  account  of  the  lung-like  nature 
of  their  air-bladder.  Wilder  shows  that  there  is  a  series  of 
forms,  mostly  Ganoids,  from  the  Amia  and  Lepidosteus  in 
which  the  pneumatic  duct  enters  the  throat  on  the  dorsal 
side,  up  to  Lepidosiren  in  which  it  enters  the  throat  on  the 
ventral  side,  like  the  air-tube  or  trachea  of  Amphibians  and 
higher  Vertebrates. 

The  breeding  habits  and  external  changes  in  form  of  the 
garpikes  have  been  described  by  Mr.  A.  Agassiz.  The  gars, 
which  are  nocturnal  in  their  habits,  appear  on  the  shores  of 
Lake  Ontario  at  Ogdensburg  in  immense  numbers  between 


MUD  FISH.  433 

the  middle  of  May  and  the  8th  of  June,  remaining  at  other 
times  of  the  year  in  deep  water. 

The  young  begin  to  hatch  about  the  end  of  May.  At 
first  the  embryo  gar  possesses  an  unusually  large  yolk-sac, 
while  the  notochord  is  very  large ;  otherwise  posteriorly  it 
resembles  the  young  of  bony  fishes.  It  differs,  however,  in 
its  large  mouth,  which  is  surmounted  with  a  hoof-shaped 
depression  edged  with  a  row  of  projecting  suckers,  by  which 
it  attaches  itself,  hanging  immovable,  to  stones  ;  the  eye  and 
brain  is  smaller  than,  in  bony  fishes.  The  tail  is  at  first 
protocercal,  beginning  on  the  second  day  to  become  hetero- 
cercal.  On  the  third  day  the  gill-covers  form  rectangular 
flaps,  and  the  first  traces  of  the  pectoral  fins  appear,  while 
the  snout  becomes  longer.  By  the  fifth  day  the  traces  of 
the  dorsal,  caudal,  and  anal  fins  appear.  When  a  little  over 
three  weeks  old  it  assumes  a  more  fish-like  form  ;  the  suck- 
ing disk  has  nearly  disappeared,  the  lower  jaw  greatly  length- 
ened, and  the  gill-covers  extend  to  the  base  of  the  pectoral 
fins.  When  between  two  and  three  weeks  old  the  young 
gar-fish  is  20  millimetres  (f  inch)  long.  The  young  rise  to  the 
surface  to  swallow  air,  as  in  the  adult.  Soon  after  this  it  is 
of  the  form  first  discovered  and  figured  by  Wilder.  The 
gar-fish,  according  to  Agassiz,  bears  some  resemblance  to 
the  sturgeon  in  certain  stages  of  growth,  and  in  the  forma- 
tion of  the  pectoral  fins  from  a  lateral  fold,  as  well  as  by  the 
mode  of  growth  of  the  gill-openings  and  the  gill-arches,  while 
it  closely  resembles  the  young  of  bony  fishes  in  the  develop- 
ment of  the  posterior  part  of  the  body,  by  the  mode  of  origin 
of  unpaired  fins  from  the  embryonic  fin-fold,  and  by  the 
mode  of  formation  of  the  fin-rays,  and  of  the  ventral 
fins. 

The  mud-fish,  Amia  calva  Linn.,  is  like  an  ordinary  bony 
fish  in  form,  with  rounded  scales ;  the  caudal  fin  "  masked 
heterocercal,"  the  snout  is  short  and  rounded,  and  the  air- 
bladder  is  large  and  cellular.  It  attains  a  length  of  two 
thirds  of  a  metre,  and  occurs  in  the  Mississippi  Valley  and 
as  far  east  as  New  York.  A  fossil  form  closely  allied  to 
Amia  dates  back  to  the  Cretaceous  Age,  and  the  genus 
Caturus  is  a  Liassic  and  Oolitic  genus. 


434  ZOOLOGY. 

Subclass  3.  Teleostei  (Bony  fishes).—  We  now  come  to  a 
type  of  fishes  which,  within  very  recent  geological  times  as 
well  as  during  the  present  period,  has  become  differentiated 
or  broken  up  into  thousands  of  species,  corresponding  to 
the  complexity  of  their  physical  environment  as  compared 
with  the  simple  features  of  the  physical  geography  of  De- 
vonian and  Carboniferous  land-masses.  Like  most  of  the 
larger  groups  of  animals,  as  the  Decapod  Crustacea,  and 
especially  the  insects,  as  well  as  the  mollusks,  the  bony 
fishes  have  attained  an  astonishing  amount  of  specialization, 
as  if  the  tree  of  icthyic  life,  taking  root  in  the  Silurian  Age, 
and  sending  out  but  a  few  branches  in  later  Palaeozoic  times, 
had  suddenly,  in  the  Cretaceous  and  Tertiary  Ages,  thrown 
out  a  multitude  of  fine  branches  and  twigs  intertwining  and 
spreading  out  in  a  way  most  baffling  to  the  systematist. 

The  essential,  diagnostic  characters  of  the  bony  fishes,  i.e., 
such  as  separate  them  from  the  Elasmobranchs  and  Ganoids, 
are  as  follows  :  The  skeleton  is  bony,  the  vertebrae  being  sep- 
arate ;  the  outer  elements  of  the  scapular  arch  are  simple,  the 
inner  elements  for  the  most  part  bony  and  usually  three  or 
two  in  number  ;  the  pectoral  fins  are  without  any  bone  rep- 
resenting the  humerus,  and  are  connected  with  the  scapular 
arch  by  several  (generally  four)  narrow  bones  (Gill).  The 
optic  nerves  cross  one  another.  The  gills  are  free,  usually 
four  on  each  side,  and  with  several  opercular  bones.  The 
heart  is  without  a  cone,  but  with  an  arterial  bulb,  and  with 
but  two  valves  at  the  origin  of  the  aorta.  The  intestine  is 
destitute  of  a  spiral  valve. 

The  student  should  dissect  a  typical  Teleost,  such  as  a 
fresh-water  or  sea  perch,  with  the  aid  of  the  following  ac- 
count of  its  anatomy.  The  drawing  and  account  here  given 
of  the  anatomy  of  the  sea-perch  have  been  prepared  by  Dr. 
C.  Sedgwick  Minot.  The  common  sea-perch  or  cunner 
(Tautogolabrus  adspersus  Gill,  Fig.  399)  resembles  the  fresh- 
water perch  very  closely  in  its  anatomy,  the  most  note- 
worthy difference  being  the  absence  of  the  coeca  at  the 
pyloric  end  of  the  stomach  in  the  marine  species  ;  with  this 
exception  the  following  description  applies  almost  equally 
well  to  the  fresh-water  perch,  so  that  this  account  will  be 


ANATOMY  OF  THE  UUNNER.  435 

available  for  western  students  who  have  not  access  to  speci- 
mens of  the  cunner. 

The  perch  has  the  general  form  of  a  flattened  spindle,  for 
it  tapers  down  at  either  end  and  is  compressed  laterally. 
There  is  no  neck  marked  off  externally,  and  the  head  ap- 
pears as  the  direct  continuation  of  the  body,  but  separated 
from  it  by  a  fissure  on  either  side  ;  this  is  the  opening  of 
the  gills,  which  extends  from  above  downwards  and  curves 
forward,  nearly  meeting  its  fellow  on  the  median  line  of  the 
under  jaw  ;  upon  opening  the  gill-slit  the  pectinate  or  comb- 
like  gills  or  branchiae  are  seen  within.  There  are  four  sets 
of  branchial  filaments,  each  set  attached  to  a  separate  de- 
scending arch,  in  front  of  each  of  which  is  a  slit  leading  into 
the  cavity  of  the  mouth  ;  but  there  is  no  slit  behind  the 
last  gill.  The  branchiae  are  protected  externally  by  the  gill- 
cover  or  operculum,  which  is  attached  in  front,  but  is  free 
behind,  where  it  forms  the  front  edge  of  the  gill-slit ;  it  is 
composed  of  four  distinct  parts  :  1.  The  praeoperculum 
nearest  the  eye,  and  with  its  lowest  corner  almost  a  right 
angle  ;  its  posterior  and  vertical  edge  is  furnished  with 
numerous  minute  projecting  spines.  2.  Appended  to  the 
underside  of  the  margin  thus  armed  is  the  operculum.  3. 
Below  the  praeoperculum  is  the  interoperculum,  which  par- 
tially covers  up  4,  the  suboperculum.  Each  of  these  parts 
has  a  separate  bony  support ;  all  four  bones  are  developed 
only  in  the  Teleosts ;  in  sturgeons,  for  example,  there  is 
only  an  operculum,  to  which  in  other  Ganoids  other  parts 
are  added ;  in  Selachians  the  whole  apparatus  remains 
undeveloped. 

The  mouth  is  placed  in  front ;  the  upper  lip  is  capable  of 
independent  motion,  being  supported  by  the  praemaxillary 
bones,  which  are  but  loosely  attached  to  the  cranium,  though 
in  many  other  fishes  the  union  is  closer.  The  eyes  are  large 
and  lidlcss  ;  just  in  front  of  each  eye  is  an  opening  of  the 
size  of  a  pin's  head  ;  these  openings  lead  into  the  nasal  sacs, 
of  which  there  are  two,  but  both  are  without  communica- 
tion with  the  mouth  ;  in  higher  vertebrates,  from  the  Dip- 
noi upwards  and  in  Myxine,  there  is  such  a  communication. 
In  the  Marsipobrancliii  there  is  but  a  single  median  nasal  sac. 


436  ZOOLOGY. 

The  ear  has  no  external  opening,  being  completely  encased 
in  bone.  Nearly  parallel  with  the  line  of  the  back  extends 
a  continuous  row  of  yellow  spots  marking  the  lateral  line 
(Fig.  399,  L),  along  which  are  found  the  pore-like  open- 
ings of  the  so-called  muciparous  glands. 

All  fish  have  fins  of  two  kinds — unpaired  and  paired  ;  the 
latter,  four  in  number,  correspond  to  the  limbs  of  other  Ver- 
tebrates. The  unpaired  fins  are  first  developed  on  a  contin- 
uous median  flap  of  integument,  which  extends  along  the 
back,  around  the  tail,  and  on  the  underside  as  far  forward  as 
the  anus  ;  cartilaginous  or  bony  rays  are  developed  in  it  as  a 
support.  In  the  adult  fish  the  fold  is  generally  discontinu- 
ous, being  usually  separated  into  three  distinct  fins — dorsal, 
caudal,  and  anal  ;  the  dorsal  fin  is  frequently,  the  anal  fin 
sometimes  subdivided.  The  fin-rays  are  (1)  either  simple 
pointed  rods,  or  (2)  jointed  and  branching.  All  the  rays  of 
the  caudal  fin,  and  the  posterior  rays  of  the  dorsal  and  anal 
fins,  are  branching.  In  some  Malacopterygians  all  the  rays 
are  branching  ;  in  many,  however,  the  first  ray  is  simple  in 
the  dorsal  and  anal  fins,  while  fishes  like  the  perch  and  cun- 
ner  are  distinguished  by  having  several  or  many  of  the  an- 
terior rays  of  the  dorsal  and  anal  fins  simple  and  pointed. 
In  the  cunner  half  the  rays  of  the  dorsal  and  the  first  two  of 
the  anal  fin  are  simple. 

The  pectoral  fins  are  attached  to  the  side  of  the  body  and 
are  large  and  rounded.  The  ventral  fins  lie  further  back 
near  the  median  ventral  line  ;  they  are  smaller  than  the  pec- 
torals. The  position  of  the  ventrals  varies  in  different  fish, 
and  is  much  used  in  classification.  The  anus  lies  immedi- 
ately in  front  of  the  anal  fin. 

The  body  is  covered  by  scales,  which  overlap  one  another 
from  before  backward  ;  their  free  edges  are  rounded  and 
smooth,  hence  they  are  called  cycloid.  These  scales,  as  in 
all  Teleosts,  are  ossifications  of  the  underlying  cutis,  and  are 
covered  by  the  epidermis  ;  they  were  formerly  wrongly  sup- 
posed to  be  epidermal  structures. 

To  dissect  a  perch  the  side-wall  of  the  mouth  must  be  re- 
moved, then  the  gill-cover  ;  study  the  arrangement  of  the 
gills.  Next  make  an  incision  along  the  median  ventral  line 


ANATOMY  OF  THE  GUNNER.  437 

from  the  level  of  the  pectoral  fins  to  just  before  the  anus,  and 
following  the  upper  edge  of  the  body-cavity  upward  and  for- 
ward cut  away  the  body-wall,  taking  care  not  to  injure  the 
large  swimming-bladder  above,  nor  the  heart  in  front.  Now 
open  the  pericardial  cavity,  which  lies  ventrally  immedi- 
ately behind  the  gills  (see  Pig.  399,  Ht).  Cut  away  the  mus- 
cular masses  around  the  back  of  the  head  ;  expose  the  cavity 
of  the  brain,  and  remove  the  loose  cellular  tissue  around  the 
nervous  centres.  If  the  gills  of  one  side  are  excised  and  the 
intestine  drawn  out,  the  dissection  will  appear  very  much  as 
in  Fig.  399. 

The  cavity  of  the  mouth  widens  rapidly  and  continues  as 
the  branchial  chamber  or  pharynx  (G),  whence  we  can  pass  a 
probe  outward  through  any  of  the  gill-slits.  There  is  a  single 
row  of  sharp-pointed  teeth  in  front  on  both  the  under  and 
upper  jaws  ;  in  the  pharynx  above  and  below  there  are 
rounded  teeth.  At  the  side  of  the  pharynx  are  the  four  gill- 
slits  and  the  four  arches  ;  the  inner  surface  of  the  anterior 
three  arches  is  smooth,  while  the  arch  behind  the  fourth  slit 
is  much  modified  in  shape  and  is  armed  with  tubercles 
and  teeth.  The  entrance  of  each  slit  is  guarded  in  front 
and  behind  by  a  row  of  projecting  tubercles  appended  to  the 
arches.  On  the  outside  of  each  arch,  except  the  fourth,  is 
a  double  row  of  filaments,  richly  supplied  with  blood-vessels 
which,  shining  through,  give  a  brilliant  red  color  to  the 
gills  ;  on  the  fourth  arch  there  is  but  a  single  row.  At  the 
upper  and  posterior  gorner  of  the  pharynx  is  the  small  open- 
ing of  the  short  oesophagus.  The  branchial  chamber  has  an 
upward  extension  on  the  sides  of  which  lie  the  pseudobran- 
chiae  (Ps),  accessory  respiratory  organs  not  connected  with 
the  gills  proper,  and  receiving  their  blood-supply  from  distinct 
arteries.  There  are  no  salivary  glands. 

The  oesophagus  dilates  almost  immediately  to  form  the 
stomach  (partly  concealed  in  the  figure  by  the  liver,  Li), 
which  seems  hardly  more  than  a  dilatation  of  the  intestine 
(In).  This  last  is  of  nearly  uniform  size  throughout,  and  after 
making  three  or  four  coils  terminates  at  the  anus,  immedi- 
ately in  front  of  the  urinary  and  genital  apertures.  When 
in  situ,  the  terminal  portion  of  the  intestine  or  the  rectum 


438  ZOOLOGY. 

extends  straight  along  the  median  ventral  line.  The  liver 
(Li)  forms  an  elongated  light-brown  mass  resting  upon  the 
stomach.  The  elongated  gall-bladder  lies  between  the 
liver  and  stomach,  somewhat  imbedded  in  the  substance  of 
the  former.  There  is  no  pancreas,  though  it  is  present  in 
some  fishes.  The  spleen  (Sp)  lies  between  the  stomach  and 
intestine,  in  the  mesentery  ;  it  is  dark  reddish-brown  in 
color. 

The  air-bladder  (S)  is  a  single  large  sac,  placed  in  the  dor- 
sal part  of  the  body-cavity.  Its  glistening  walls  are  com- 
posed mainly  of  tough  fibrous  tissue.  The  pneumatic  duct, 
by  which  the  bladder  communicates  with  the  oesophagus  in 
many  fishes,  is  wanting  in  the  perch  as  in  nearly  all  other 
Teleosts.  The  air-bladder  normally  contains  only  gases.  It 
conceals  most  of  the  kidneys,  which  extend  the  whole  length 
of  the  body-cavity  on  either  side  of  the  middle  line,  as  two 
long  strips  of  a  deep  though  dull  red.  They  project  beyond 
the  air-bladder  in  front  (Ki)  and  behind  (AY).  Their  an- 
terior ends  are  somewhat  separated  from  one  another  by  the 
intervening  pharynx.  The  ureters  open  into  a  urinary 
bladder  (U)  behind  the  anus. 

The  ovary  is  single  and  varies  greatly  in  size  according  to 
the  season.  In  the  male  the  sexual  glands  are  double.  Each 
testis  ( ri )  is  an  elongated,  whitish,  lobulated  organ,  placed  im- 
mediately below  the  swimming-bladder,  and  continues  pos- 
teriorly with  the  spermiduct,  which  opens  immediately  be- 
hind the  anus. 

The  heart  (Ht)  lies  in  the  triangular  pericardial  cavity ;  it 
consists  of  two  portions,  the  dark-colored  venous  chamber, 
or  auricle,  above,  and  the  lighter-colored  arterial  chamber,  or 
ventricle,  below.  The  auricle  receives  from  above  two  large 
veins,  one  from  either  side  ;  these  veins  are  called  the  ducti 
Cuvieri.  Each  Cuvierian  duct,  as  can  be  seen  in  the  figure, 
ascends  beside  the  oesophagus,  and  there  receives  a  large  jug- 
ular vein  from  in  front,  and  a  large  cardinal  vein  from  be- 
hind. Furthermore,  a  large  vein,  the  sole  representative  of 
the  vena  cava  of  higher  Vertebrates,  passes  from  the  liver, 
near  its  anterior  end,  through  the  pericardium,  and  empties 
into  the  Cuvierian  ducts  near  their  common  auricular  orifice. 


ANATOMY  OF  THE  GUNNER. 


439 


The  walls  of  the  auricle  are  comparatively  thin  ;  the  auriculo- 
ventricular  orifice  is  provided  with  valves,  which  prevent 
the  blood  flowing  back  into  the  auricle.  The  walls  of  the 
ventricle  are  thick  and  very  muscular  ;  from  the  upper  end 
of  the  ventricle  close  to  the  base  of  the  auricle  springs  the 
bulbus  arteriosus,  a  muscular  cylinder,  which,  running  hori- 
zontally forward,  passes  out  through  the  pericardium,  and  is 
continued  as  the  less  muscular  aorta  (^4)  underneath  the 
branchial  arches  along  the  median  line  ;  the  aorta  gives  off 
branches  on  both  sides,  one  to  each  arch  to  supply  the  bran- 
chiae ;  the  vessels  after  ramifying  are  gathered  together,  to 
again  form  a  single  trunk,  which  passes  backward  immedi- 


Ps 


tn 

* 


Fig.  399.— Anatomy  of  the  Gunner,  male.  Z,  lateral  line  ;  fft,  heart ;  G,  pharynx  ;  Ps, 
pseudobranchia  ;  Sp,  spleen  ;  S,  air-bladder ;  Ki,  Ki',  kidneys  ;  bl,  bladder  ;  T,  tes- 
tis  ;  A,  aorta  ;  B,  brain  ;  In,  intestine  ;  Zi,  liver  ;  0,  gills.— Drawn  by  C.  S.  Minot. 

ately  underneath  the  spinal  column  ;  it  is  called  the  descend- 
ing aorta. 

The  body  and  pericardial  cavities  are  called  serous,  because 
their  lining  membranes  are  always  moist  with  serum,  a  watery 
fluid,  very  much  like  blood-plasma.  The  lining  of  the  body- 
cavity  is  named  the  peritoneum,  and  forms  a  continuous  cov- 
ering around  the  viscera.  It  is  important  to  observe  that  the 
various  organs  simply  project  into  the  body-cavity  and  do 
not  lie  really  inside  of  it.  In  fishes  we  find  the  disposition  of 
the  parts  to  correspond  more  closely  with  the  fundamental 

pe  of  Vertebrate  structure  than  it  does  in  higher  forms,  in 
which  further  modifications  have  supervened.  The  pharynx 
still  has  its  distinctive  character  ;  the  pericardium  lies  at  the 


440  ZOOLOGY. 

base  of  the  neck,  instead  of  in  the  thorax  as  in  the  higher  Ver- 
tebrates. The  heart  still  preserves  its  primitive  division  ;  on 
the  other  hand,  the  swimming-bladder  is  a  special  adaptation 
of  the  piscian  type,  while  the  frequent  absence  of  the  pan- 
creas is  a  peculiarity  of  fishes  the  meaning  of  which  is  not 
yet  understood. 

The  brain  (B)  does  not  occupy  the  whole  of  the  cranial 
cavity,  but  is  imbedded  in  a  large  accumulation  of  cellular 
tissue.  In  order  to  study  the  brain  satisfactorily,  it  should 
be  exposed  from  above,  laying  bare  at  the  same  time  the  optic 
nerves  and  muscles.  The  two  olfactory  lobes  are  followed 
by  two  lobes  (H),  the  cerebral  hemispheres,  and  immediately 
behind  them  two  larger  lobes  (Q),  the  corpora  bi-  or  quadri- 
gemina  (optic  lobes,  not  optic  thalami) ;  further  back  follows 
a  single  median  lobe  (Cb),  the  cerebellum,  somewhat  conical 
in  shape  and  resting  upon  the  medulla  oblongata  (M),  from 
which  spring  various  nerves,  and  which,  tapering  backward, 
is  continued  as  the  spinal  cord.  In  front  appear  the  very  large 
and  conspicuous  optic  nerves  (Op),  the  right  nerve  passing 
obliquely  to  the  left  eye,  the  left  nerve  to  the  right  eye 
running  under  the  right  nerve,  but  forming  no  chiasma; 
each  optic  nerve  is  a  plaited  membrane,  folded  somewhat 
like  a  fan  when  shut  up,  an  arrangement  occurring  only 
among  fishes.  In  a  side-view  of  the  brain  (Fig.  400,  7>),  the 
mode  of 'origin  of  the  optic  nerves  and  their  origin  from  the 
optic  lobes  can  be  clearly  seen  ;  it  further  shows  the  various 
forms  of  the  lobes  of  the  brain,  and  the  large  inferior  lobes 
(L)  below  the  corpora  quadrigemina  ;  these  lobes  are  very 
remarkable  and  difficult  to  homologize. 

The  eyes  lie  in  two  sockets,  separated  by  an  interorbital 
septum  (Fig.  400,  S).  The  eyeball  has  the  form  of  an  ob- 
late spheroid,  and  is  moved,  as  in  all  Vertebrates,  by  four 
recti  and  two  obliqui  muscles.  The  recti  spring  from  around 
the  exit  of  the  optic  nerve  from  the  brain-case,  and  thence 
diverge  to  be  inserted  into  different  parts  of  the  eyeball ; 
above  is  the  rectus  superior  (Rs)  ;  towards  the  interorbital 
septum  (S)  rectus  internus  (Ri),  opposed  to  the  last  is  the 
rectus  externus  (Re),  and  below  is  the  rectus  inferior,  not 
shown  in  the  figure.  In  Teleosts  both  oblique  muscles,  the 


ANATOMY  OF  THE  CUNNER. 


441 


superior  ( Os)  and  inferior  ( Oi),  arise  from  the  front  of  the 
orbit  near  the  interorbital  septum.     The  disposition  of  the 


Oi, 


A. 


Fig.  400.— Anatomy  of  the  brain  of  the  dinner,  dor.-al  and  side  view.    JB,  01,  olfac- 
tory lobes  ;  the  crura  and  the  thalami  not  represented.— Drawn  by  C.  S.  Minot. 

recti  is  very  constant,  but  the  obliqui  vary  considerably  in 
their  origin  in  different  Vertebrates. 

If  a  perch  be  cut  through  transversely,  so  that  the  section 
passes  through  the  fore-part  of  the 
air-bladder,  and  the  anterior  portion 
then  looked  at  from  behind,  a  very 
instructive  view  will  be  obtained,  as 
in  Fig.  401.  The  best  sections  can  be 
made  by  first  freezing  the  fish.  The 
vertebral  column  ( V)  appears  a  little 
above  the  middle  ;  overlying  it  is  the 
neural  canal  with  the  spinal  cord  ;  im- 
mediately below  it  is  the  descending  or 
dorsal  aorta  (Ao),  on  either  side  of 
which  follow  the  kidneys  (K),  resting 
directly  upon  the  air-bladder  (Bt). 
Lowermost  is  the  body-cavity,  with 
the  stomach  (#),  and  intestine  (In), 
surrounded  by  the  liver,  which  has  g^conner.-.Drawn  by  c. 
been  almost  entirely  removed.  The 

rest  of  the  section  is  occupied  by  muscles,  which,  it  will  thus 
be  seen,  make  up  the  main  bulk  of  the  body.     (Minot.) 


442  ZOOLOGY. 

The  so-called  "  mucous  canal"  or  lateral  line  of  fishes  and 
Amphibians  is  sensory.  It  consists  of  small  masses  of 
nerve-epithelium,  arranged  in  linear  series  along  the  sides  of 
the  head  and  body,  having  hair-cells  continuous  with  nerves. 
They  are  called  "nerve-buttons"  or  "  nerve-heaps."  Accord- 
ing to  Schultze,  their  office  appears  to  be  to  appreciate  mass- 
movements  of  the  water,  and  more  particularly  vibrations, 
which  have  longer  periods  than  those  appreciated  by  the  ear 
(Dercum).  In  the  blind-fish  of  the  Mammoth  Cave  a  row 
of  sense-papillae  is  situated  on  the  front  of  the  head,  sup- 
plied with  nerve-fibres  sent  from  the  fifth  pair  of  nerves 
(Wyman). 

The  angler  (Lophius  piscatorius)  has  long  been  known  to 
possess  hinged  teeth,  capable  of  being  bent  inward  toward 
the  mouth,  but  by  virtue  of  the  elasticity  of  the  hinge  at 
once  resuming  the  upright  position  when  pressure  is  removed 
from  them.  Andbleps  and  Pcecilia  have  also  movable  teeth. 
The  hake,  a  voracious  predatory  fish,  and  in  a  less  degree 
other  Gadidce,  are  possessed  of  hinged  teeth. 

The  nature  of  respiration  is  intimately  connected  with  the 
production  of  sounds  by  fishes.  Recent  researches  by  Jobert 
on  certain  unusual  modes  of  breathing  in  fishes  are  of  special 
interest.  He  has  examined  certain  fishes  of  the  Amazons, 
i.e.,  species  of  CallicMhys,  Doras,  Erithrinus,  Hypostomus 
and  Sudisgigas  or  "pirarucu"  of  the  natives,  the  latter  being- 
allied  to  the  herring.  In  the  Callichtliys  the  intestine  is  trans- 
formed into  a  respiratory  organ.  When  the  water  dries  up 
it  emigrates  to  other  pools  or  streams,  creeping  by  means 
of  its  pectoral  fins.  This  fish  can  live  twenty-four  hours 
out  of  the  water  with  impunity. 

In  the  gigantic  pirarucu,  the  swimming-bladder  is  a  long 
sac,  and  the  upper  part  does  not  look  like  that  organ,  being 
spongy,  areolar,  reddish  -  brown,  friable,  and  intimately 
pressed  to  the  dorsal  and  lateral  walls  of  the  body ;  its  color 
recalls  that  of  the  lungs  of  a  bird,  and  functionally  it  re- 
sembles the  latter. 

Among  accessory  breathing  organs  are  the  lamellate  cavity 
of  the  Anabas,  and  the  sac-like  appendages  which  are  in  con- 
nection with  the  gill-cavity,  and  extend  under  the  muscles 


MUSICAL  FISH.  443 

of  the  body  of  Amphipnous  cucliia,  Gymnarchus  and  Sacco- 
branchus  singio. 

The  noises  produced  by  certain  fishes  are  due  primarily  to 
the  action  of  the  pneumatic  duct  and  swimming-bladder, 
while  different  kinds  of  noises  are  made  accidentally  or  in- 
voluntarily by  the  lips  or  the  pharyngeal  or  intermaxillary 
bones,  as  in  the  tench,  carp  and  a  large  number  of  other 
fishes.  Over  fifty  species  of  fish  are  known  by  Dufosse  to 
produce  sounds  of  some  sort,  and  Abbot  has  increased  the 
number  in  this  country.  The  swimming-bl adders  of  Trigla 
and  Zeus  have  a  diaphragm  and  muscles  for  opening  and 
closing  it,  by  which  a  murmuring  sound  is  made.  The 


Fig.  402  -Gizzard  Shad. 

loudest  sounds  are  made  by  Pogonias  cJiromis,  the  drum- 
fish.  In  some  Cyprininw,  Siluroids  and  eels  the  sound  is 
made  by  forcing  the  air  from  the  swimming-bladder  into  the 
oesophagus.  In  the  sea-horse  (Hippocampus),  the  sounds 
are  made  by  the  vibrations  of  certain  small  voluntary 
muscles. 

Dr.  C.  0.  Abbot  has  in  this  country  discovered  that  the  mud 
sun-fish  (Acantharchus  pomotis)  utters  a  deep  grunting  sound; 
the  gizzard  shad  (Dorosomacepedianum,  Fig.  402)  makes  "an 
audible  whirring  sound  ;"  the  chub-sucker  or  mullet  (Erimy- 
zon  oblong  am)  "utters  a  single  prolonged  note  accompanied 
by  a  discharge  of  air-bubbles ;"  the  cat-fish  (Amiurus  lynx) 


444  ZOO  LOG  Y. 

produces  "a  gentle  humming  sound  ;"  eels  utter  a  more  dis- 
tinctly musical  sound  than  any  other  of  those  observed  by 
Abbot,  who  states  that  "  it  is  a  single  note,  frequently  re- 
peated, and  has  a  slightly  metallic  resonance."  It  should 
also  be  noticed  that  the  organs  of  hearing  in  many  musical 
fishes  are  said  to  be  unusually  well  developed,  hence  these 
sounds  are  probably  love-notes ;  and  Abbot  notices  the  fact 
that  these  fishes  are  dull-colored  during  the  reproductive  sea- 
son, as  well  as  at  other  times,  while  voiceless  fishes,  such  as 
the  perch,  common  sun-fish,  chub,  roach,  etc.,  are  highly 
colored  during  the  breeding  season,  and  thus  the  sexes  are 
mutually  attracted  in  the  one  case  by  music,  and  in  the  other 
by  bright  colors.  Finally  the  sounds  of  fishes  may  be  said 
to  be  homologous  with  those  of  reptiles,  birds  and  mammals, 
the  air-bladder  being  homologous  with  the  lungs  of  the 
higher  Vertebrates,  while  the  pneumatic  duct  is  comparable 
with  the  trachea  of  birds  and  mammals. 

In  swimming,  the  propelling  motion  is  mainly  exerted  by 
the  tail,  the  movements  of  which  are  somewhat  like  those  of 
an  oar  in  sculling.  The  spines  of  the  tail -fin  are  movable, 
and  are  capable  of  being  brought  into  such  a  position  that 
the  fin  will  meet  with  less  resistance  from  the  water  while 
the  tail  is  bent,  then  straightened,  and  it  is  when  being 
straightened  that  the  fish  is  propelled.  The  movements  of 
the  pectorals  and  ventrals  are  to  steady  the  fish  and  to  ele- 
vate and  depress  it,  while  the  dorsal  and  anal  fins  steady 
the  body  and  keep  it  upright,  like  a  dorsal  and  ventral  keel. 

Among  viviparous  bony  fishes  are  certain  Cyprinodonts 
(as  Anableps  and  Pcecilia),  the  eel-like  Zoarces,  and  the 
blind-fish  of  the  Mammoth  Cave.  A  small  family  of  Cali- 
fornian  marine  fishes,  in  form  resembling  the  sun-fish  (Pomo- 
tis)  are  called  by  Agassiz  Embiotocidce,  from  the  fact  that 
they  bring  forth  their  young  alive.  Embiotoca  Jacksoni 
Agassiz,  which  is  twenty-seven  and  a  half  centimetres  (10-J 
inches)  long,  has  been  known  to  produce  nineteen  young, 
each  about  seven  and  a  half  centimetres  (3  inches)  long. 

During  their  reproductive  season,  many  bony  fishes,  such 
as  the  stickleback,  salmon,  and  pike,  are  more  highly  colored 
than  at  other  times,  the  males  being  especially  brilliant  in 


DEVELOPMENT  OF  FISH.  445 

their  hues,  while  other  secondary  sexual  characters  are  devel- 
oped. The  female  deposits  her  eggs  either  in  masses  at  the 
surface  of  the  water,  as  the  goose-fish,  or  at  the  bottom 
on  gravel  or  sand  as  do  most  other  fishes,  the  male  passing 
over  them  and  depositing  his  "  milt"  or  spermatic  particles. 
The  egg  has  a  thin  transparent  shell,  and  the  yolk  is  small, 
covered  with  a  thick  layer  of  the  "  white." 

The  eggs  after  fertilization  undergo  partial  segmentation, 
the  primitive  streak,  notochord,  nervous  cord,  and  brain  de- 
velop as  in  the  chick,  but  that  the  embryo  is  to  become  a 
fish  is  soon  determined  by  the  absence  of  an  amnion  and  allan- 
tois,  and  by  the  fact  that  the  germ  lies  free  over  the  yolk 
like  a  band. 

In  the  pike  the  heart  begins  to  beat  about  the  seventh  day, 
and  by  this  time  the  alimentary  canal  is  marked  out.  The 
primitive  kidneys  are  developed  above  the  liver.  The  air- 
bladder  arises  as  an  offshoot  opposite  the  liver  from  the  ali- 
mentary canal,  and  the  gall-bladder  is  also  originally  a 
diverticulum  of  the  intestine.  The  urinary  bladder  in  the 
fish  is  supposed  to  be  the  homologue  of  the  allantois  of  the 
higher  Vertebrates.  The  principal  external  chan  ge  is  the 
appearance  of  the  usually  large  pectoral  fins. 

The  embryo  pike  hatches  in  about  twelve  days  after  devel- 
opment begins,  and  swims  about  with  the  large  yolk-bag 
attached,  and  it  is  some  seven  or  eight  days  before  the  young 
fish  takes  food,  living  meanwhile  on  the  yolk  mass.  The 
perch  hatches  in  twelve  days  after  the  egg  is  fertilized,  and 
swims  about  for  eight  or  ten  days  before  the  yolk  is  absorbed. 
The  gills  gradually  develop  with  the  absorption  of  the  yolk. 

The  tail  in  most  bony  fishes  is  at  first  protocercal,  then 
becoming  heterocercal  as  in  the  adult  sharks,  but  subse- 
quently, after  the  fish  has  swam  about  for  a  while  and  in- 
creased in  size,  it  becomes  homocercal  or  symmetrical.  The 
scales  are  the  last  to  be  developed. 

In  the  large  size  of  the  pectoral  fins,  the  position  of  the 
mouth,  which  is  situated  far  back  under  the  head,  the  hetero- 
cercal tail,  the  cartilaginous  skeleton  and  uncovered  gill- 
slits,  the  embryo  salmon,  pike,  perch,  etc.,  manifest  transi- 
tory characters  which  are  permanent  in  sharks. 


44C  ZOOLOGY. 

The  bony  fishes  date  back  to  the  Jurassic  period,  but  did 
not  become  numerous  until  the  Cretaceous  and  especially  the 
Tertiary  Period.  The  Green  River  beds  of  Wyoming  abound 
in  their  remains. 

The  Teleosts  are  divided  into  eight  orders,  in  an  ascending 
series  as  follows  :  Opisthomi,  Apodes,  Nematognathi,  Scyplio- 
phori,  Teleocephali,  Pediculati,  Lopliobranchii  and  Plectog- 
nathi. 

Order  1.  OpiMomi. — The  fishes  of  this  group  are  char- 
acterized by  the  separation  of  the  shoulder-girdle  from  the 
head.  The  ventral  fins  are  either  abdominal  or  wanting. 
The  typical  genus  is  Notocantlius,  in  which  the  body  is  elon- 
gated, with  a  proboscis-like  snout. 

Order  2.  Apodes. — In  this  group,  also,  the  scapular  arch 


Fig.  403.— Common  Eel,  Anguitta,  acutirostris. 

is  free  from  the  skull,  while  the  maxillary  bones  are  rudi- 
mentary. The  branchial  apertures  are  unusually  small,  and 
there  are  no  ventral  fins,  while  the  body  is  very  long,  cylin- 
drical, snake-like.  The  order  is  represented  among  many 
other  forms  by  the  common  eel  (Anguilla),  the  conger-eel, 
and  the  Murcena  of  the  Mediterranean  Sea.  The  conger-eel 
(Conger  oceanicus  Gill)  ranges  from  Newfoundland  to  the 
West  Indies.  Gill,  as  well  as  Giinther  and  others,  regards  a 
long  transparent  ribbon-like  fish,  described  under  the  name 
of  Leptoceplialus  as  the  young  of  the  conger-eel. 

The  common  eel,  Anguilla  acutirostris  (Fig.  403),  occurs 
on  both  sides  of  the  Atlantic,  on  the  North  American  coast 
as  far  south  as  Cape  Hatteras,  and  in  inland  rivers  and  lakes. 
The  sexes  do  not  differ  externally,  and  internally  only 


BREEDING  HABITS  OF  THE  EEL.  447 

as  regards  the  form  of  the  reproductive  glands.  The 
ovaries  form  two  ribbon-like  masses  extending  from  the 
liver  to  just  beyond  the  vent  and  attached  by  one  edge 
to  the  walls  of  the  body,  with  the  free  edge  hanging 
downwards.  When  in  spawn  the  ovary  is  very  thick, 
white,  and  the  eggs  can  be  seen  with  the  naked  eye, 
being  nearly  one  half  millimetre  in  diameter.  When  ripe 
they  break  through  the  wall  of  the  gland  and  drop  into 
the  body-cavity,  there  being  no  oviduct,  and  pass  out  of  the 
genital  opening  situated  directly  behind  the  vent.  The  male 
glands  occupy  the  same  position  as  the  ovaries  of  the  female, 
but  are  smaller,  narrower,  and  distinctly  lobulated.  Out  of 
about  six  hundred  specimens  of  eels,  only  four  males  have 
yet  been  found  in  this  country.  These  had  testes  like  those 
described  by  Syrski  in  the  Italian  eel  (A.  vulgar  is),  while  Pack- 


Fig.  404.— A  Siluroid  Fish,  Ariue.    Young  with  the  yolk  not  absorbed. 

ard  detected  the  mother  cells,  and  Mr.  Kingsley  observed  mov- 
ing active  spermatozoa.  It  is  probable  that  the  eel  descends 
rivers  in  October  and  November,  spawning  in  the  autumn  and 
early  winter  at  the  mouth  of  rivers,  and  in  harbors  and  es- 
tuaries in  shallow  water.  By  the  end  of  the  spring  the 
young  eels  are  two  or  three  inches  long,  and  then  ascend 
rivers  and  streams.  They  grow  about  an  inch  a  month,  and 
the  females  do  not  spawn  at  least  before  the  second  year,  *.  0. , 
when  about  twenty  inches  long.  Mr.  Mather  estimates  that 
the  ovary  of  an  eel  weighing  six  pounds  when  in  spawn  con- 
tains upwards  of  9,000,000  eggs. 

Order  3.  Nematognathi. — This  group  is  represented  in 
North  American  waters  by  the  catfish  and  horned  pout. 
The  name  of  the  order  (from  v^jnaf  njfiiaros,  thread,  and 


448 


ZOOLOGY. 


yraOos,  jaw)  is  in  allusion  to  the  filaments  or  barbels  grow- 
ing out  from  the  jaws,  and  which  are  characteristic  of  the 
members  of  the  group.  The  upper  jaw  is  formed  by  the 

intermaxillary  bones  only,  while 
the  supra-maxillary  bones  form 
the  bases  of  the  large  barbels. 
The  suboperculum  is  always  ab- 
sent, as  is  also  the  symplectic  ; 
the  supra-occipital  and  parietal 
bones  are  co-ossified.  The  skin  is 
either  naked  or  with  bony  plates. 
The  air-bladder  connects  by  a 
duct  with  the  roof  of  the  oesoph- 
agus. While  a  few  forms  are 
marine,  most  of  the  Siluroid 
fishes  are  inhabitants  of  the  riv- 
ers of  tropical  countries,  a  large 
number  being  characteristic  of 
the  rivers  of  Brazil.  All  the 
North  American  species  belong  to 
the  family  Siluridw,  of  which 
the  common  representatives  are 
the  horned  pout  and  western 
catfish.  In  these  forms  the  skin 
is  naked.  The  horned  pout, 
Amiurus  atrarius  Gill,  ranges 

from  New  England  to  Maryland 
and  the  Great  Lakeg>  jt  breedg  in 

New  England  in  holes  in  gravel  during  the  midsummer.  The 
Great  Lake  catfish,  Amiurus  nigricans  Lesueur,  is  abundant 
in  the  Great  Lakes,  and  is  about  a  metre  (2-4  feet)  in  length. 
The  blind  catfish,  Gronias  nigrilabris  Cope,  inhabits  a  sub- 
terranean stream  tributary  to  Conestoga  River  in  Eastern 
Pennsylvania. 

Among  the  exotic  South  American  Siluroids  are  Arius 
(Fig.  404)  and  Aspredo  (Fig.  405)  of  Guiana.  In.  Arius  and 
some  of  its  allies  in  South  America  the  eggs  are  carried  by 
the  males  in  their  mouth,  from  five  to  twenty  being  thus 


Bules  attached  by  slight  stalks. 


EGYPTIAN  ELECTRICAL  FISH.  449 

borne  about  until  the  young  hatch.  They  are  probably 
caught  up  after  exclusion  and  fertilization.  Some  of  these 
eggs  are  half  an  inch  in  diameter.  Dr.  Day  states  that  the 
same  habits  occur  in  certain  Indian  species  of  Arius  and 
Osteogeniosus.  A  species  of  Arius  was  found  by  Stein- 
dachner,  at  Panama,  to  carry  its  eggs  in  a  fold  of  the  skin  of 
its  belly ;  afterwards  the  males  bear  them  about  in  their 
mouth. 

The  females  of  Aspredo  have  on  the  ventral  surface 
horny,  stalked  capsules,  which  contain  eggs  from  one  to  two 
millimetres  in  diameter  ;  the  capsules  disappear  as  soon  as 
the  young  hatch. 

Malapterurus  electricus  Lacepede,  of  the  Nile,  is  electri- 
cal, the  electric  cells  forming  a  layer  directly  beneath  the 
skin  and  enveloping  the  whole  body,  except  the  head  and 
fins.  The  cells  are  minute,  lozenge-shaped,  about  one  and 
a  half  millimetres  in  diameter.  They  are  supplied  by  a 
nerve  from  the  spinal  cord.  The  shock  is  comparatively 
feeble,  but  suffices  for  defence,  (£  the  fish  being  protected  by 
its  electrifying  coat,  as  is  the  hedgehog  by  its  spines." 
(Owen.) 

Order  4.  Scypliophori. — This  order,  first  named  and 
characterized  by  Cope,  derives  its  appellation  from  the 
Greek  ffnvcpos,  a  bowl,  and  (pepoo,  to  bear,  in  allu- 
sion to  a  peculiarity  of  the  pterygoid  bone,  which  is  en- 
larged, funnel-shaped,  and  excavated  by  a  bowl-like  cham- 
ber which  expands  laterally  and  is  covered  by  a  lid-like  bone. 
The  brain  has  a  peculiar  plicated  organ  over  the  cerebellum  ; 
the  air-bladder  is  simple,  communicating  by  a  duct  with  the 
intestinal  canal.  The  order  comprises  two  families,  the 
members  of  which  inhabit  the  rivers  of  Africa  ;  they  are  the 
MormyridcB,  represented  by  a  number  of  genera  and  species, 
and  the  Gymnarcliidce,  of  which  Gymnarclius  niloticus  is 
the  only  known  species. 

Order  5.  Teleocephali. — These  are  our  common  types  of 
fishes,  and  are,  whether  we  consider  their  individual  struc- 
ture or  the  number  of  specific  forms,  the  most  highly  de- 
veloped, i.  e.,  specialized,  of  the  class.  The  name  is  derived 
from  rf'Aezos,  perfect,  and  *f<pttAf?,  head,  in  allusion  to  the 


450  ZOOLOGY. 

high  degree  of  elaboration  and  diversity  in  the  bones  of  the 
head.  The  skeleton  is  usually  completely  ossified.  The 
bones  of  the  skull  and  of  the  jaws  are  fully  developed.  The 
lower  jaw  is  attached  to  the  skull  by  a  suspensorium  of  sev- 
eral well-marked  bones,  including  a  symplectic,  while  the 
hyoid  and  gill  arches  are  well  developed,  as  is  the"  scapular 
arch.  The  brain  has  small  olfactory  lobes  and  a  small  cere- 
bellum. The  scales  are  generally  present,  and  either  cte- 
noid (i.e.,  rough-edged)  or  cycloid  (i.e.,  rounded  but  smooth 
on  the  edge).  The  common  examples  are  the  carp,  herring, 
trout  and  salmon,  pike,  perch,  cod,  and  flounder. 

Turning  now  to  some  of  the  more  characteristic  members 
of  the  order,  we  first  notice  one  of  the  lowest  Teleosts,  the 
electrical  eel  (Gymnotus  electricus  Linn.)  of  South  Amer- 
ica, which  is  two  metres  in  length,  and  is  characterized  by 
its  greatly  developed  electrical  batteries.  These  are  four  in 
number,  situated  two  on  each  side  of  the  body,  and  together 
form  nearly  the  whole  lower  half  of  the  trunk.  The  plates 
of  the  cells  are  vertical  instead  of  horizontal,  as  in  the  tor- 
pedo, while  the  entire  batteries  or  cells  are  horizontal,  in- 
stead of  vertical,  as  in  the  electrical  ray.  The  nerves  sent 
to  the  batteries  of  the  eel  are  supplied  by  the  ventral 
branches  of  about  two  hundred  pairs  of  spinal  nerves. 

Succeeding  these  and  allied  forms  are  the  herrings  (Clu- 
peidce\  represented  by  the  common  English  herring,  Clupea 
Jiarengus  Linn.,  which  inhabits  both  sides  of  the  North 
Atlantic,  extending  on  the  American  side  from  the  polar 
regions  to  Cape  Cod;  the  ale  wife,  Pomolobus  pseudoharengus 
Gill,  which  ranges  from  Newfoundland  to  Florida  ;  the  shad, 
Alosa  sapidissima  Storer,  which  has  the  same  geographical 
distribution  as  the  alewife  ;  and  the  menhaden  or  pogy, 
Brevoortia  tyrannus  Goode,  which  extends  from  the  coast 
of  Maine  to  Cape  Hatteras.  These,  with  the  cod,  hake, 
haddock,  salmon,  and  a  few  other  species,  comprise  our 
most  valuable  marine  food-fishes.  The  fisheries  of  the 
United  States  yield  about  $9,000,000  annually,  whilst  those 
of  Great  Britain  amount  to  about  $8,000,000,  and  those  of 
Norway  about  $14,000,000. 

The  herring  is  a  deep-water  fish  which  visits  the  coast  in 


HABITS  OF  THE  HERRING  AND  SHAD.          451 

spring  in  immense  schools,  in  which  the  females  are  three 
times  as  numerous  as  the  males,  to  spawn,  selecting  shoal 
water  from  three  to  four  fathoms  deep  in  bays,  where  the 
eggs  hatch.  At  this  season,  and  early  in  the  summer,  hun- 
dreds of  millions  are  caught,  especially  on  the  Canadian, 
Newfoundland,  and  Labrador  coasts.  The  English  white- 
bait is  the  young  of  the  herring.  The  herring  is  caught  in 
deep  nets  with  meshes  large  enough  to  capture  individuals 
of  ordinary  size,  the  nets  having  a  finer  mesh  than  those 
used  for  the  mackerel  fishery. 

The  alcwife  and  shad  are  said  to  be  anadromous,  from 
their  habit  early  in  spring  of  visiting  the  coast  and  ascend- 
ing rivers  in  vast  numbers  to  spawn.  The  eggs  are  of  mod- 
erate size  ;  the  ovaries  are  said  to  contain  about  25,000,  and 


Fig.  411.— The  Herring,  Clupea  harengus,  one  third  natural  size.— From  the  Ameri- 
can Naturalist. 

at  times  as  many  as  100,000  or  150,000  eggs.  They  are  dis- 
charged near  the  surface,  sinking  slowly  to  the  bottom. 
The  time  between  impregnation  and  hatching  varies  from 
about  three  to  six  days,  according  to  the  temperature.  The 
shad  eats  little  or  nothing  in  fresh  water,  being  then  engaged 
in  the  act  of  reproduction.  In  the  sea  they  live  on  small 
Crustaceans,  such  as  Mysis,  etc.  The  menhaden  is  now  put 
up  as  a  substitute  for  sardines,  and  is  of  great  value  as  fish- 
bait,  especially  in  the  mackerel  fishery,  and  for  its  oil. 

The  family  Salmonidce  comprise  the  salmon,  trout,  and 
whitefish,  with  a  number  of  species  and  varieties.  The 
species  of  the  genus  Salmo  have  not  more  than  eleven  rays 
to  the  anal  fin,  while  the  salmon  of  the  west  coast,  quinnat, 


452  ZOOLOGY. 

has  fifteen  or  sixteen  anal  rays.  The  tialmo  solar  Linn, 
sometimes  weighs  eighty  pounds.  It  is  common  to  Europe 
as  well  as  Northeastern  America.  In  the  autumn  the  salmon 
ascends  rivers  to  spawn,  penetrating  as  near  the  source  as 
possible.  During  the  breeding  season  the  males  differ  de- 
cidedly from  the  females,  in  the  long,  slender,  hooked  snout, 
the  body  being  thin  and  high-colored.  The  eggs  are  very 
large,  exceeding  a  pea  in  size,  and  are  laid  in  shallow  holes 
made  in  the  gravel  of  streams.  The  extreme  young  are 
banded  and  called  parr ;  when  about  a  year  old,  and  of  a 
bright  silvery  color,  before  descending  the  rivers  to  the  sea, 
it  is  called  a  smoU  ;  after  its  return  from  the  sea  into  fresh 
water  it  goes  by  the  name  of  grilse ;  and  finally,  after  re- 
turning a  second  time  from  the  sea,  it  assumes  its  name  of 
salmon.  The  trout,  Salmo  (Salvelinus)  fontinalis  Gill  and 


Fig.  412.— The  Smelt—  Osmerus  mordax— one  half  natural  size.— From  the  Amer- 
ican Naturalist. 

Jordan,  also  breeds  in  the  autumn  and  early  winter ;  it  is 
not  anadromous,  living  permanently  in  streams  and  ponds. 

An  allied  family  embraces  the  smelts,  Osmerus  eper- 
lanus  Linn.,  and  0.  mordax  Mitchill,  which  live  on  both 
sides  of  the  Atlantic,  and  range  from  Nova  Scotia  to  Vir- 
ginia. The  capelin,  Mallotus  villosus  Cuvier,  is  valuable 
as  bait  in  the  cod  fishery.  It  spawns  in  the  summer.  The 
males  are  distinguished  by  a  prominent  lateral  ridge  along 
the  sides  of  the  body  and  are  more  numerous  than  the 
females. 

Belonging  to  the  same  suborder  or  group  of  families 
as  the  SalmonidcB  is  the  family  Galaxiidce,  represented  by 
Galaxias  and  Neochanna  (Fig.  413),  in  the  latter  of  which 
the  ventral  fins  are  absent. 


BLIND  FISH.  453 

The  carps  (Cyprinus),  shiners  and  minnows  abound  every- 
where in  the  Northern  States  in  ponds  and  weedy  streams.  The 
breeding  habits  of  the  dace  (Rliiniclitliys  atronasus  Mitchill) 
have  been  observed  by  Dr.  Gregg.  The  females  spawn  over 
"nests"  or  shallow  depressions  two  feet  in  diameter  in  run- 
ning brooks  about  a  foot  deep ;  the  male  passes  over  the 
eggs  fertilizing  them ;  then  the  pair  bring  small  pebbles 
which  are  dropped  over  the  eggs,  until  layer  after  layer  alter- 


Fig.  413. — Neochanna. — From  Liitken. 

nately  of  eggs  and  pebbles  are  deposited,  when  a  heap  is 
formed,  the  young  hatching  out  and  remaining  among  the 
pebbles  until  old  enough  to  venture  out  into  the  stream. 
The  dace  is  closely  allied  to  the  chub  (Semotilus  rliotheus 
Cope,  Fig.  415).  Succeeding  them  are  the  suckers  (family 
Catostomidcz)  of  which  Catostomus  teres  Lesueur  is  an  ex- 
ample. 

The  blind  fish  of  the  Mammoth  and  other  caves,  and  of 


Fig.  414.— Mud-Minnow.— From  Abbot. 

adjoining  wells  connecting  with  subterranean  streams,  are 
remarkable  for  the  rudimentary  state  of  the  eyes,  and  con- 
sequently of  color.  There  are  several  species,  the  most 
common  and  largest  being  Amblyopsis  spelceus  De  Kay  ;  this 
species  is  viviparous.  Representing  the  family  UmbridcB  is 
the  mud-minnow  (Melanura  limi  Kirt.,  Fig.  414). 

The  flying-fish  represent  another  family.     Their  pectoral 
fins  are  very  broad  and  large.     They  dart  from  the  water 


454 


ZOOLOGY. 


with  great  speed  without  reference  to  the  course  of  the  wind 
and  waves.  They  make  no  regular  flying  motions  with  their 
pectoral  and  ventral  fins,  but  spread  them  out  quietly, 
though  very  rapid  vibrations  can  be  seen  in  the  outstretched 
pectoral  fins.  They  usually  fly  farther  against  the  wind  than 
with  it,  or  if  their  track  and  the  direction  of  the  wind  form 
an  angle.  Most  flying-fish  which  fly  against  or  with  the 
wind  continue  in  their  whole  course  of  flight  in  the  same  di- 
rection in  which  they  come  out  of  the  water.  Winds  which 
blow  from  one  side  on  to  the  original  track  of  the  fish  bend 
their  course  inward.  All  fish  which  are  at  a  distance  from 
the  vessel  hover  in  their  whole  course  in  the  air  near  the  sur- 
face of  the  water.  If  in  strong  winds  they  fly  against  the 


Fig.  415.— The  Large  Chub,  Semotilua  rhothews,  one  fifth  natural  size.— From  Abbot. 

course  of  the  waves,  then  they  fly  a  little  higher  ;  sometimes 
they  cut  with  the  tail  into  the  crest  of  the  waves.  Only 
such  flying-fish  rise  to  a  considerable  height  (at  the  highest, 
by  chance,  five  metres  above  the  surface  of  the  sea)  whose 
course  in  the  air  becomes  obstructed  by  a  vessel.  In  the 
daytime  flying-fish  seldom  fall  on  the  deck  of  the  ship,  but 
mostly  in  the  night ;  never  in  a  calm,  but  only  when  the 
wind  blows.  (Moebius.) 

Following  the  flying-fish  is  the  family  represented  by  the 
silver  gar  or  bill-fish  (Belone  longirostrus  Mitchill,  Fig.  416). 

The  sucker  (EcTieneis  remora  Linn.)  occurs  along  the 
whole  coast  of  the  United  States,  and  is  found  all  over  the 


HABITS   OF  THE  PERCH,  ETC. 


455 


tropical  and  subtropical  seas.  It  is  provided  with  a  broad 
oval  sucker  on  the  upper  side  of  the  head,  by  which  it  ad- 
heres to  other  fish  or  even  to  ships,  and  may  thus  be  trans- 
ported long  distances.  Another  noticeable  member  of  the 
order  is  the  blue-fish  (Pomatomus  saltatrix  Linn.,  Fig.  417), 
so  valuable  as  a  food-fish. 


Fig.  416.— The  Bill-fish,  Belone  longirostms.—From.  the  American  Naturalist. 

The  dolphin  (Coryphcena,}  is  sometimes  found  upon  our 
coast,  but  it  is  essentially  a  pelagic  fish,  occurring  only  out 
of  sight  of  land  upon  the  high  seas.  The  pilot-fish  is  also 
a  pelagic  form. 

The  percoid  fishes  are  represented  by  the  perch  (Percafiu- 
viatilis  Linn.),  which  spawns  in  winter,  making  slight  hol- 
lows in  the  gravel  in  shoal  places  in  ponds  ;  their  movements 


Fig.  417.— The  Blue-fish,  Pomatomus  saltatrix,  one  sixth  natural  size.— From  the 
American  Naturalist. 

can  be  watched  through  the  ice.  On  the  other  hand,  the 
sun-fish  or  bream  (Eupomotis  aureus  G.  and  J.)  spawns  in 
the  summer  time,  making  a  nest,  which  they  scoop  out  of 
the  river  bottom.  The  banded  sun-fish  (MesogonistiuS  clm- 
todon  Gill)  occasionally  scoops  out  a  little  basin  in  the  sand, 
in  which  it  deposits  its  eggs  late  in  the  spring.  The  spotted 


456 


ZOOLOGY. 


sun-fish  (Enneacanthus  obesus  Gill,  Fig.  418)  lives  in  muddy 
streams,  burying-  itself  in  the  mud  in  winter.  Of  similar 
mud-loving  habits  is  the  mud-minnow  (Melanura  limi 
Agassiz),  which  spawns  in  the  spring.  The  pirate  perch 
(ApJiredoderus  sayanus  De  Kay)  occupies  the  nest  of  com- 


Fig.  418.— The  Spotted  Sun-fish,  Enneacanthus  obesus.— After  Abbot. 

mon  sun-fish,  and  with' the  female  guards  it  and  afterwards 
the  young  till  they  are  nearly  a  centimetre  (two-fifths  inch) 
in  length,  when  they  are  left  by  their  parents.  (Abbot.) 

The  darters,  JZtheostomidce,  belong  near  the  perches,  and 
comprise  the  smallest  of  fishes.  They  inhabit  the  streams 
of  the  Mississippi  Valley.  A  common  example  is  the  sand- 
darter  (Pleurolepis  pellucidus  Agassiz,  Fig.  419). 


Fig.  419.— Saud-Darter.— After  Jordan. 


The  male  stickleback  (Gasterosteus)  makes  an  elaborate 
nest  of  leaves,  etc.,  suspended  in  mid-water,  within  which  it 
remains  watching  the  eggs  and  young. 

One  of  the  most  valuable  food-fishes  is  the  mackerel 
(Scomber  scombrus  Linn.,  Fig.  420),  whose  range  is  from 


HABITS  OF  THE  MACKEREL.  457 

Greenland  to  Cape  Hatteras.  It  remains  in  deep  water  dur- 
ing the  late  autumn  and  winter,  approaching  the  coast  in 
May  and  June  for  the  purpose  of  spawning,  its  annual 
appearance  being  very  regular.  The  number  of  eggs  de- 
posited in  one  season  by  each  female  is  said  to  be  from  five 
to  six  hundred  thousand.  After  spawning  they  move  north- 
ward, following  the  coast  until  they  are  checked  by  the 
coolness  of  the  water,  when  they  return,  and  in  November 
seek  the  deep  water  again.  When  spawning  they  do  not 
take  the  hook  ;  they  are  then  lean  ;  but  at  the  time  of  their 
departure  from  the  coast  they  are  fat  and  plump.  (Blake.) 
The  eggs  of  the  mackerel  as  well  as  of  the  cod  are  so  light 
as  to  rise  to  the  surface,  where  they  develop.  Allied  to  the 
mackerel,  though  of  great  size,  are  the  horse-mackerel  and 
the  sword-fish,  whose  upper  jaw  is  greatly  prolonged. 


Fig.  420. — The  Mackerel,  Scomber  scombrus,  one  quarter  natural  size  — After  Blake. 

The  singular  Anabas  of  the  East  Indies  is  the  representa- 
tive of  a  small  group  of  fishes  called  Labyrinthici  or  laby- 
rinth-fishes, in  allusion  to  a  cavity  on  the  upper  side  of  the 
branchial  cavity  on  the  first  gill-arches,  containing  a  laby- 
rinthine organ,  which  consists  of  thin  plates,  developed 
from  the  upper  pharyngeal  bones,  enabling  the  fish  to  live 
for  a  long  time  out  of  water.  Analas  scandens  Cuvier,  of 
the  fresh  waters  of  India,  will  travel  over  dry  land  from  one 
pond  to  another,  and  is  even  said  to  climb  .trees  by  means 
of  the  spines  in  its  fins. 

Near  the  head  of  the  order  stands  the  cunner  (Tautogola- 
brus  adspersus  Gill),  whose  anatomy  is  represented  by  Figs. 
404-40G  Passing  over  the  tautog,  the  voracious  wolf-fish 
(Anarrhichas),  the  blennies  (Blennidce),  in  which  the  body 


458  ZOOLOGY. 


is  long  and  narrow,  and  the  viviparous  eel-pout  (Zoarces),  the 
cottoids  or  sculpijis,  and  a  number  of  allied  forms,  we  come 
to  the  hake  (Merlucius  Ulinearis  Gill),  the  haddock  (Melano- 
grammus  ceglefinus  Gill,  Fig.  421),  and  cod  (Gadus  morrhua 


421.—  The  Haddock,  Melanogrammw  ceglefinus.—From.  the  American  Nat- 


Linn., Fig.  42£),  all  of  which  extend  northwards  from  Cape 
Hatteras,  the  cod  abounding  on  both  sides  of  the  Atlantic, 
being  a  circumpolar  fish.  The  cod  does  not,  as  formerly 
supposed,  migrate  along  the  coast,  but  seeks  the  cool  tempe- 
rature to  which  it  is  adapted  by  gradually  passing  in  the 


Fig.  422.— The  Cod-fish,  Gadus  morrhua.— from  the  American  Naturalist. 

early  summer  from  shallow  to  deep  water,  and  returning  as 
the  season  grows  colder.  It  visits  the  shallow  water  of  Mas- 
sachusetts Bay  to  spawn  about  the  first  of  November,  and 
towards  the  last  of  the  month  deposits  its  eggs.  About 


ASYMMETRY  OF  THE  FLOUNDER.  459 

eight  or  nine  million  of  eggs  are  annually  deposited  by  each 
female.  (Blake.)  The  eggs  laid  by  the  co.d  rise  to  the  sur- 
face of  the  water,  on  which  they  float.  The  young  fish 
hatch  on  the  New  England  coast  in  twenty  days  after  they 
are  extruded.  Several  millions  of  cod  were  artificially  hatched 
at  Gloucester,  Mass.,  in  the  winter  of  1878-9,  by  the  United 
States  Fish  Commission ;  it  has  thus  been  demonstrated 
that  this  fish  can  be  artificially  propagated. 

The  cod  is  the  most  important  of  all  the  food-fishes, 
whether  we  consider  the  number  taken  and  the  amount  of 
capital  involved  in  the  cod-fishery.  It  abounds  most  on 
the  Grand  Banks  of  Newfoundland.  The  breeding  habits 
of  the  haddock,  hake  and  pollock  are  probably  like  those  of 
the  cod. 

Fierasfer  is  a  small  eel-like  fish,  with  a  long,  thin  tail.  It 
is  typical  of  a  peculiar  family,  and  is  noteworthy  from  being 
a  "  commensal"  or  boarder  in  the  digestive  canal  of  Holo- 
thurians,  etc.  F.  acus  Briinn.  lives  in  Holuthurians,  and 
another  species  in  a  star-fish  (Culcita).  The  BrotulidcB  are 
fishes  allied  to  the  cod,  but  constituting  a  distinct  family. 
Most  of  them  are  salt-water  species,  but  allied  forms  (Luci- 
fuga  suUerraneus  and  Stygicola  dentata)  live  in  subterra- 
nean waters  in  Cuba. 

At  the  head  of  Teleocepliali  stand  the  flounders,  halibut 
and  soles,  which  are  an  extremely  modified  type  of  the  order. 
In  these  fishes  the  body  is  very  unsymmetrical,  the  fish  vir- 
tually swimming  on  one  side,  the  eyes  being  on  the  upper 
side  of  the  head.  The  upper  side  is  colored  dark,  due  as  in 
other  fishes  to  pigment-cells  ;  the  lower  side  is  colorless,  the 
pigment-cells  being  undeveloped.  When  first  hatched  the 
body  of  the  flounder  is  symmetrical,  and  in  form  is  some- 
what cylindrical,  like  the  young  of  other  fishes,  swimming 
vertically  as  they  do,  and  with  pigment-cells  on  the  under- 
side of  the  body.  Steenstrup  first  showed  by  a  series  of 
museum  specimens  that  the  flounder  was  not  born  with  the 
eyes  on  the  same  side  of  the  head,  but  that  one  eye  gradually 
passed  from  the  blind  to  the  colored  side.  Mr.  A.  Agassiz 
has  studied  the  process,  and  finds  that  the  transfer  of  the  eye 
from  the  blind  side  to  the  colored  side  occurs  very  early  in 


460  ZOOLOGY. 

life,  while  all  the  facial  bones  of  the  skull  are  still  cartilagi- 
nous, long  before  they  become  hard  and  ossified,  i.e.,  when 
the  flounder  (Plagusia)  is  twenty-five  millimetres  (one  inch) 
long.  "The  transfer  of  the  eye  from  the  right  side  to  the 
left  takes  place  by  means  of  a  movement  of  translation,  ac- 
companied and  supplemented  by  a  movement  of  rotation 
over  the  frontal  bone."  Young  flounders,  when  less  than 
two  inches  in  length,  are  remarkably  active  compared  with 
the  adults,  darting  rapidly  through  the  water  after  their 
food,  which  consists  principally  of  larval,  surface-swimming 
crustaceans,  etc.  (A.  Agassiz. )  The  common  flounder  from 
Nova  Scotia  to  Cape  Hatteras  is  Pseudopleuronectes  Ameri- 
canus  of  Gill. 


Fig.  423.— Goose-fish,  one  tenth  natural  size.— From  Tenney's  Zoology. 

Order  6.  Pediculati. — The  type  of  this  order  is  the  goose- 
fish.  The  name  was  given  to  the  group  from  the  long 
slender  bones  supporting  the  pectoral  fins.  The  gill-open- 
ings are  small  and  placed  in  axils  of  the  pectoral  fins.  Lo- 
pliius piscatorius  Linn.,  the  goose-fish  or  angler  (Fig.  423), 
has  an  enormous  mouth,  and  swallows  fishes  nearly  as  large 
as  itself.  The  head  and  fore-part  of  the  body  is  very  large*, 
the  skin  is  naked,  scaleless.  Its  eggs  are  laid  in  broad, 
ribbon-like,  thin  gelatinous  masses,  two  metres  long  and 
half  a  metre  wide,  which  float  on  the  surface  of  the 
ocean. 

Order  7.  Lophobramhii.  —The  tufted-gilled  fish — such  the 
name  of  the  order  indicates — have  a  fibro-cartilaginous  skele- 


THE  PIPE  FISH. 


461 


ton ;  a  single  opercular  bone,  while  the  snout  and  lower 
jaw  are  prolonged  into  a  tube,  with  the  mouth  at  the 
end.  The  chief  peculiarity,  however,  is  the  gills,  which  are 
developed  in  the  form  of  a  row  of  tufted  lobes  on  each  side 
of  the  branchial  arches.  The  scales  are  large,  forming  an- 
gular plates  arranged  in  longitudinal  rows  (Gill).  In  Sole- 
nostoma  of  the  Indian  Ocean  the  female  carries  the  eggs  in 
a  pouch  formed  by  the  union  of  the  ventral  fins  with  the 
integument  of  the  breast. 

The  male  of  the  pipe-fish  (Syngnathus  peckianus  Storer) 
receives  from  the  female  the  eggs,  and  carries  them  in  a 
small  pouch  under 
his  tail,  which  is 
open  beneath 
through  its  whole 
length.  This  sin- 
gular mode  of  mas- 
culine gestation  is 
still  farther  per- 
fected in  the  sea- 
horse (Hippocam- 
pus hudsonius  De 
Kay,  Fig.  424), 
which  lives  off- 
shore from  Cape 
Cod  to  Cape  Hat- 

teras).       The  pOUCh        .     FiS-  484.— Sea-horse,  male,  with  the  young  issuing 
. '  from  the  brood-pouch.— After  Lockwood. 

is  situated  on   the 

breast.  The  male,  by  simple  mechanical  pressure  of  its 
tail,  or  by  rubbing  against  some  fixed  object,  as  a  shell, 
forces  the  fry,  to  the  number  of  about  a  thousand,  out  of  its 
brood-pouch,  the  young  at  this  time  measuring  about  twelve 
millimetres  (5-6  lines)  in  length.  In  the  young  the  head  is 
at  first  rounded,  the  snout  being  short  and  blunt  (Lockwood). 
Order  8.  Plectognathi. — This  group,  represented  by  a  few 
singular  forms,  such  as  the  trunk-fish,  file-fish,  puffers,  and 
sun-fish,  is  characterized  by  the  union  of  the  bones  of  the 
upper  and  especially  the  lower  jaws.  There  are  few  verte- 
brae, the  scales  are  often  modified  to  form  spines,  and  the 


462 


ZOOLOGY. 


ventral  fins  are  usually  absent.  They  are  inhabitants  of  warm 
waters.  The  trunk-fish  or  box-fish,  Lactophrys  trie/onus 
Poey,  is  a  West  Indian  fish ;  one  specimen  has  appeared  at 
Holmes'  Hole,  Mass.  The  porcupine  -  fish  (ChilicUJiys 
turgidus  Gill)  and  smooth  puffer  (Tetrodon  Icevigatus  Gill) 
and  the  spring  box-fish  (Chilomycterus  geometricus  Kaup) 


Fig.  425.— Sun-fish,  Mold  rotunda^  one  eighteenth  natural  size.— After  Putnam. 

range  from  Cape  Cod  to  Florida.  The  sun-fish  (Mola  ro- 
tunda Cuvier,  Fig.  425)  is,  like  the  others  of  the  order,  a 
surface  -  swimmer.  It  is  sometimes  a  metre  or  more  in 
length,  weighing  five  hundred  pounds  or  more.  Allied 
forms  are  Ortliagoriscus  oblongus  (Fig.  426)  and  the  globe- 


CLASSIFICATION  OF  FISHES. 


463 


fish,  Molacanthus  Pallasii  (Fig.  427),  which  occur  in  the 
North  Atlantic. 


Fig.  426.—  Orthagori&CMS  (Mangus>  young,  natural 
size.— After  Harting. 


Pig.  427.—  Mola- 
canthus Pallasii, 
half  grown,  natural 
size.  —  After  Put- 
nam. 


CLASS  III.— PISCES. 

Aquatic  Vertebrates  with  a  movable  lower  jaw,  a  cartilaginous  or 
osseous  skeleton,  with  paired  and  unpaired  fins  supported  by  fin  rays  ; 
no  sternum;  usually  covered  with  scales;  breathing  by  gills.  Heart 
with,  a  single  ventricle  and  auricle.  Mostly  oviparous. 

Subclass  I.  Elasmobranchii. —  Skeleton  cartilaginous  ;  skull  without 
membrane  bones,  five  to  seven  pairs  of  gill-sacs  and  gill- 
openings  ;  no  opercular  bones ;  tail  heterocercal ;  scales 
placoid ;  heart  with  a  pulsating  aortic  bulb ;  optic  nerves 
forming  a  chiasma ;  intestine  with  a  spiral  valve ;  both 
oviparous  and  viviparous. 

Order  1.  Plagiostomi  (Selache,  Lamna,  Raia). 
Order  2.  HolocepJiali  (Chimaera). 

Subclass  II.  Oanoidei. — Skeleton  cartilaginous  or  ossified  ;  skull  with 
plate-like  membrane  bones ;  one  pair  of  gill-openings  cov- 
ered by  opercular  bones ;  skin  usually  with  cycloid  or  gan- 
oid scales ;  air-bladder  with  a  pneumatic  duct ;  embryos  or 
young  sometimes  with  external  gills  ;  chiasma  of  the  optic 
nerves ;  intestine  with  a  spiral  valve  ;  development,  so  far 
as  known,  much  as  in  the  sharks,  and  in  some  respects  like 
the  bony  fishes  ;  the  living  forms  oviparous. 

Order  1.  Chondroganoidei  (Acipenser). 
Order  2.  Dipnoi  (Ceratodus,  Lepidosiren). 


464  ZOOLOGY. 

Order  3.  BrancMoganoidei  (Polypterus). 
Order  4.  Hyoganoidei  (Lepidosteus,  Amia). 

Subclass  III.  Teleostei.— Skeleton  bony;  skull  composed  of  numerous 
bones  ;  optic  nerves  crossing  each  other  ;  usually  four  pairs 
of  gills,  with  several  opercular  bones ;  heart  without  a  cone, 
but  with  an  arterial  bulb ;  intestine  generally  without  a 
spiral  valve  ;  mostly  oviparous. 

Order  1.  Opisthomi  (Notacanthus). 

Order  2.  Apodes  (Anguilla). 

Order  3.  Nematognathi  (Amiurus). 

Order  4.  Scyphophori  (Mormyrus). 

Order  5.  Teleocepliali  (Salmo,  Perca,  Gadus). 

Order  6.  Pediculati  (Lophius). 

Order  7.  Lophobranchii  (Hippocampus). 

Order  8.  PlectognatM  (Tetrodon,  Mola). 

Laboratory  Work.— Fishes  should  usually  be  dissected,  except  when 
large,  under  the  water ;  small  specimens  can  be  pinned  down  to  the 
bottom  of  cork-  or  wax-lined  dissecting  pans,  and  the  more  delicate 
parts  worked  out  with  fine  scissors  and  knives.  The  brain  and  spinal 
cord  can  be  dissected  with  ease,  provided  care  be  taken,  with  scalpel 
and  scissors,  as  the  bones  covering  them  can  be  cut  away  by  means  of 
stout  scissors  and  bone-pliers  and  fine  surgical  saws.  Longitudinal 
sections  will  bring  out  the  relations  of  the  brain  and  'beginnings  of  the 
nerves,  and  transverse  sections  of  the  tail  may  be  made  to  show  the 
disposition  of  the  muscles.  The  skeleton  may  be  prepared  whole  by 
removing  the  flesh  carefully  from  alcoholic  or  partly  macerated  speci- 
mens. Disarticulated  skeletons  for  study  can  be  made  by  parboiling 
the  fish  and  then  separating  the  bones  from  the  flesh.  To  study  the 
circulation,  careful  injections  should  be  made  by  the  use  of  an  inject- 
ing syringe,  with  wax,  plaster  of  Paris,  or  vermilion  as  the  injecting 
medium. 


CLASS  IV. — BATEACHIA  (Salamanders,  Toads,  and  Frogs). 

General  Characters  of  Batrachians. — We  have  had  an- 
ticipations of  the  Batrachians  or  Amphibia  in  the  Ganoids, 
especially  the  Dipnoan  fishes,  which  it  will  be  remembered 
approach  the  members  of  the  present  class  in  the  lung-like 
nature  of  the  air-bladder  and  in  the  presence  of  external 


ANATOMY  OF  BATRAGHIANS.  465 

gills  in  the  young,  as  well  as  in  the  form  of  the  skull,  there 
being  many  bony  parts  in  the  skull  which  resemble  similar 
parts  in  Batrachia.  Indeed  so  close  in  some  characters  is  the 
approximation  of  the  fishes  to  the  Batrachians,  that  the  two 
classes  have  been  placed  in  a  series  called  Ichtliyopsida.  The 
Batrachians,  however,  differ  essentially  from  the  fishes  in  hav- 
ing the  bones  of  the  skull  few,  directly  comparable  with 
those  of  reptiles,  birds,  and  mammals,  and  in  being  jointed 
to  the  vertebral  column  by  two  articular  surfaces  called  con- 
dyles,  the  first  vertebra,  or  atlas,  having  two  corresponding 
articulating  hollows.  The  limbs  have  the  same  number  of 
subdivisions,  with  distinct  leverage  systems,  as  the  higher 
Vertebrates,  the  bones  composing  them  being  closely  homol- 
ogous. True  ribs  now  appear.  Some  have  persistent  exter- 
nal* gills,  and  all  have  well-developed  lungs.  So  that  for  the 
first  time  we  have  the  coexistence  of  true  limbs  and  lungs 
in  animals  which  are  air-breathing  and  move  about  freely  on 
land,  though  from  passing  a  part  of  their  adult  life  in  or 
about  fresh  water  they  are  said  to  be  amphibious.  The  skin 
is  usually  scaleless.  The  circulation  is  incompletely  double, 
there  being  sometimes  two  auricles.  Like  fishes,  they  are 
cold-blooded.  They  are  mostly  oviparous,  a  few  are  vivipa- 
rous, and  nearly  all  undergo  a  metamorphosis. 

To  enter  more  into  detail  :  The  vertebrae  of  Batrachians 
are  in  the  living  Proteus  and  allies,  and  in  the  blind-worms 
(Apoda)  biconcave  ;  in  the  salamanders  and  in  the  Surinam 
toad  (Pipa)  and  BomMnator  they  are  concave  behind,  but 
in  the  toads  and  frogs  generally  they  are  for  the  most  part 
concave  in  front,  but  vary  in  diiferent  parts  of  the  spinal 
column,  some  of  the  same  individuals  being  biconvex  and 
others  biconcave.  "While  the  vertebras  are  numerous  in  the 
tailed  forms,  in  the  tailless  toads  and  frogs  there  are  but 
eleven,  two  in  the  coccyx,  one  in  the  sacrum,  the  remaining 
eight  forming  the  rest  of  the  column.  In  the  frog,  when 
the  tail  disappears,  a  long,  spine-like  piece  (Fig.  428,  e)  called 
the  urostyle  is  developed  from  the  rudiments  of  a  few  verte- 
brae. In  the  extinct  Arcliegosaurus  the  bodies  of  the  verte- 
brae are  but  little  ossified ;  in  Trimerorhachis  they  are  rep- 
resented by  the  bony  rings  of  three  segments,  while  in  allied 


466  ZOOLOGY. 

Labyrinthodonts  such  as  RUacliitomus,  the  vertebrae  are 
ossified,  but  the  centra  consist  of  three  pieces.  In  Cricotus 
there  are  two  kinds  of  bodies,  centra  and  inter  centra.  The 
ribs  are  rudimentary,  except  in  the  blind-worms  (Ccecilid). 
The  skull  is  usually  broad  and  flattened  ;  it  differs  from 
that  of  fishes  in  having  no  bones  representing  the  operculum, 
suboperculum,  interoperculum,  or  branchiostegal  bones  ;  but 
a  membrane  bone  probably  homologous  with  the  preopercu- 
lum  is  said  to  exist.  The  maxillary  are  usually  and  the  prc- 
maxillary  bones  always  present,  usually  armed  with  teeth  ;  no 
Batrachian  possesses  a  complete  basioccipital,  supraocci- 

pital,  basisphenoid,  ali- 
sphenoid,  or  presphe- 
noid  cartilage  bone; 
while  "the  frog's  skull 
is  characterized  by  the 
development  of  a  very 
singular  cartilage  bone, 
called  by  Cuvier  the  '  os- 
en  ceinture,'  or  girdle- 
bone. v  (Huxley.) 

The  embryonic  carti- 
lage persists  in  the  low- 
er jaw  in  adult  Batra- 
chians  as  in  fishes,  and 

Fig.  428.-Skeleton  of  a  Frog,    a,  skull ;  6,  bony  parts  ai'6  developed 

vertebrae;   c,  sacrum,  and   e,  its   continuation  .        •>  *  .  •«»••. 

(urostyle);/,suprascapula;  <7,humerus;  A,  fore-  m    Connection     With     it 
arm  bones ;  i,  wrist  bones  (carpals  and  meta-  .  .   .... 

carpals) ;   d,  ilium  ;  m,  thigh  (femur) ;   n,  leg  which   essentially  COrre- 
bone  (ulna) ;   o.  elongated  first  pair  of  ankle-  -,   ,       . ,  £  r>  -i 

bones  (tarsais)  ;  p,  y,  foot  bones  or  phalanges.  Spond  to  those  of  lishes. 

(Gegenbaur.) 

The  suspensorium  is  immovably  joined  to  the  skull,  and 
with  it  is  connected  the  hyoidean  arch.  The  branchial 
arches  in  the  tailed  forms  persist  in  varying  numbers,  i.  e., 
from  two  to  four,  but  are  dropped  in  the  toads  and  frogs.  The 
skulls  of  certain  Labyrinthodonts  are  roofed  in  by  broad, 
flat  bones,  so  that  they  bear  a  strong  resemblance  to  certain 
Ganoids  represented  by  the  garpike,  while  Gegenbaur  states 
that  there  are  many  bony  parts  in  the  skull  of  the  Batra- 
chians  which  resemble  those  in  the  Dipnoan  fishes.  The  ex- 


ANATOMY  OF  BATRACHIANS.  467 

tinct  ArcUegosaurus  had  in  its  larval  life  branchial  arches, 
and  in  fact  so  close  are  the  affinities  of  some  Amphibians  to 
the  Ganoids  that  it  is  probable  that  both  types  have  had  a  com- 
mon origin  ;  while  on  the  other  hand  the  bones  of  certain 
extinct  scaly  Labyrinthodonts  have  been  regarded  by  some 
authors  as  reptiles  ;  for  example,  the  Carboniferous  Mastodon- 
saurus  was  described  as  a  reptile,  but  has  been  referred  to 
the  Amphibians  by  modern  writers. 

The  sternum  or  breast-bone  (Fig.  429,  s)  first  appears  in 
the  Batrachians.  The  shoulder-girdle  is  in  great  part  carti- 
laginous. In  the  toads  and 
frogs  (Anura)  the  fore  limbs, 
the  radius,  and  ulna,  and  in 
the  hind  limbs  the  tibia  and 
fibula,  grow  together  ;  there 
are  four  toes  in  the  fore  feet, 
and  five  toes  in  the  hind  feet. 
In  the  Siren  the  hind  legs  are  Pig.  429.-sternum  and  ehouider-girdio 

won  tin  «•  •  in  tlio  pnncrn  <annVp«  of  Fro«  (8™®  lemporaria}.  p,  body  of 
Wanting  ,  111  Hie  jngO-snaK.es  the  8ternum  ;  «?,  scapula  ;  sc',  supra-scap- 
tlio  limhq  nrp  ula  °,  co,  coracoid-bone,  fused  in  the  mid- 

tne     imus    aie  d]e  ]ine  with  Itg  fe]low  of  the  opp0!5ite 


either  two  or  three-toed.  sidc  («>;  ^cia™le  ***  epistenmm.  The 

extreme  shaded  double  portion  below  p 

The    teeth    of    modern    Ba-   is  the  sdphittentam.     The  cartilaginous 
.  parts  are  shaded.  —After  Gegenbaur. 

trachians  are  conical  or  lobate, 

and  microscopically  are  simple,  while  those  of  the  extinct 
forms  are'mostly  complicated  by  the  labyrinthine  infolding 
of  the  walls,  as  seen  in  microscopic  sections  ;  the  teeth  of 
many  Ganoids  have  a  similar,  though  much  simpler  struc- 
ture. They  are  usually  of  the  same  size,  and  may  be  ar- 
ranged on  projecting  portions  of  different  bones  of  the  mouth, 
i.e.,  the  premaxillary,  maxillary,  mandibular,  vomerine,  pal- 
atine, and  pterygoid  bones,  as  in  fishes.  In  tadpoles  and 
in  Siren  the  jaw-bones  are  encased  in  horny  beaks  like  those 
of  turtles  and  birds.  In  many  Labyrinthodonts  two  tusks 
were  developed  on  the  palate.  The  nasal  canal  is  much  as 
in  the  Dipnoan  fish,  the  internal  opening  being  situated  in 
the  Perennibranchiates  just  within  the  soft  margin  of  the 
mouth.  In  the  salamanders  and  frogs  it  is  bordered  with 
firmer  parts  of  the  jaw.  The  labyrinth  of  the  ear  is  large, 
and  the  tympanum  or  drum  of  the  ear  is  external,  Am- 


468 


ZOOLOGY. 


phibians  having  a  middle  ear  in  addition  to  the  internal  ear 
of  fishes.  In  toads  and  frogs  the  tongue  is  quite  free  and 
capable  of  being  protruded,  except  in  Pipa  and  Dactyle- 
thra,  where  it  is  entirely  wanting.  In  other  forms  the 
tongue  is  much  as  in  fishes,  not  being  capable  of  extension 

from  the  mouth.  As  in 
fishes,  there  are  no  salivary 
glands.  The  gills  of  Am- 
phibians consist  of  two  or 
three  pairs  of  branched, 
fleshy  appendages,  which 
grow  out  from  as  man} 
arches.  While  in  the  toad 
and  frog  the  gills  are  small 
and  remain  but  for  a  short 
time,  in  the  larval  salaman- 
ders, especially  the  axolotl 
(Fig.  430),  the  gills  are  still 
longer  retained,  while  in 
the  mud-puppy  (Necturus) 
they  persist  throughout  life. 
The  digestive  canal  is  us- 
ually simple,  straight,  there 
being  no  enlargement  form- 
ing a  stomach  ;  in  other 
species,  both  tailless  and 
tailed,  the  canal  dilates  into 
a  stomach,  which  in  the 
toad  lies  across  the  body- 
cavity.  In  tadpoles,  which 
live  on  decaying  vegetable 

m  offov     +Tio    rlirroafivo    -rvnnf 
matter>    tne    CllgeStlVC    tiact 

ef  va;nBenedeennding  aorta--From  Gervais  is  very  long  and  closely  coil- 

ed  (Fig.  431). 

The  lungs  are  long,  slender  sacs,  much  like  those  of  the 
Dipnoan  Lepidosiren,  which  extend  backwards  into  the  ab- 
domen, as  in  the  lizards  and  snakes,  no  diaphragm  existing 
to  confine  them  in  a  thoracic  cavity.  The  larynx  exists  in 
a  very  rudimentary  state,  though  the  vocal  powers  of  the 


rom  which  the  vascular  arches  (Z?)  origi- 
nate;  66,  branchial  vein;  the  lower  A,  vena 


ANATOMY  OF  BATRACHIANS. 


469 


toads  and  frogs  are   so  highly  developed.     The  trachea  is 
short. 

The  heart  has  two  auricles,  the  right  one  the  larger,  and  a 
single  ventricle ;  but  in  Proteus  the  auricles  connect  with 
each  other,  and  in  the  salamanders  there  is  a  hole  in  the  par- 
tition separating  the  auricles.  There  are  also  indications  of 


Fig.  433.— Tadpole  of  a  Frog.    1, 
vena  cava ;  2,  left  auricle  ;   3,  pul- 
jin  and  its  origin  in  the 
;  4,  left  auricle :  5,  ven- 


Fig.  431.— Mouth  and  digestive 
canal  of  a  Tadpole.  A,  mouth  ;  6, 
intestine  coiled  on  itself  ;  c,  liver  ; 
d,  hepatic  duct ;  e,  pancreas ;  /, 
rudimentary  hind  legs  ;  g,  rectum. 
—After  Gervais  and  Van  Beneden. 

a  partition  in  the  ventricle.  Fig. 
432  represents  the  circulatory  or- 
gans of  a  tadpole,  after  the  gills 
have  become  absorbed,  and  before 
the  aortic  arches  are  reduced  in 
number. 

The  nervous  system  is  much 
as  in  reptiles  ;  but  the  optic  lobes 
are  rather  small  ;  the  cerebrum  is  small.  The  kidneys  are 
in  many  respects  like  those  of  fishes,  especially  sharks,  as 
is  the  internal  reproductive  system.  The  ovaries  are  greatly 
enlarged  during  the  breeding  season.  The  sperm  is  usually 
passed  to  the  kidney,  and  thence  through  the  ureters  out  of 
the  cloaca.  The  oviducts  and  ureters  have  a  common  outlet 


branchial  veins ;  9,  aorta ;  10,  pul- 
monary artery  and  its  subdivisions 
in  the  lungs.— After  Gervais  and  Van 
Beneden. 


470  ZOOLOGY. 

into  the  cloaca.  In  the  salamanders  the  end  of  the  oviduct 
serves  as  a  uterus.  There  are  also  fat-bodies  (Fig.  433)  at- 
tached to  the  anterior  end  of  the  reproductive  glands  of  the 
toads  and  frogs,  the  use  of  which  is  unknown.  For  a  gene- 
ral idea  of  the  structure  of  Amphibians  the  student  should 
dissect  a  frog  or  toad  in  connection  with  the  following  de- 
scription and  accompanying  illustration  (Fig.  433),  prepared 
by  Dr.  C.  S.  Minot. 

The  frog  is  one  of  the  types  of  Vertebrates  most  valuable 
to  the  student,  being  readily  obtained  and  easily  dissected. 
The  accompanying  figure  represents  the  anatomy  of  the 
spotted  or  leopard  frog,  Rana  lialecina,  male. 

The  skin  is  smooth,  having  neither  scales,  feathers,  nor 
hairs,  and  contains  numerous  microscopic  glands,  of  which 
there  are  said  to  be  two  kinds— one  having  an  acid,  the  other 
an  alkaline  secretion  (L.  Hermann).  It  is  pigmented  on 
the  dorsal  surface,  but  whitish  underneath.  The  head  is 
broad,  triangular,  with  two  large  nasal  openings  in  front, 
large  and  prominent  eyes,  two  tympanic  membranes  formed 
by  a  part  of  the  integument  stretched  across  a  hard  ring, 
and  an  enormous  mouth.  The  neck  is  short  and  not  con- 
stricted. The  body  tapers  slightly  posteriorly,  and  has  the 
opening  of  the  cloaca  upon  the  posterior  end  of  its  back. 
Each  limb  consists  of  the  three  divisions  :  in  the  front  leg, 
Irachium,  antebrachium,  and  manus  with  four  digits,  of 
which  the  fourth  is  very  much  thickened  in  the  male  ;  the 
sexes  may  be  distinguished  by  this  mark.  In  the  hind  leg 
the  three  divisions  are  the  femur,  crus,  and  pes,  with  five 
long  digits,  between  which  the  membranous  web  is  stretched. 
If  the  web  is  examined  in  a  living  frog  with  a  microscope, 
the  circulation  of  the  blood  in  the  capillaries  can  be  studied. 
The  current  of  corpuscles  and  plasma  is  constant,  and  in  a 
given  vessel  passes  only  in  one  direction  ;  by  following  the 
stream  backwards  and  forwards  it  will  be  found  to  issue 
from  larger  vessels,  the  arteries,  and  to  enter  into  other  and 
different  vessels,  the  veins.  The  pigment  corpuscles  can 
also  be  seen  in  the  web  ;  they  are  branching  bodies,  capable 
of  drawing  in  or  expanding  their  processes,  and  they  can  be 
made  to  contract  by  an  electrical  shock  from  an  induction 
apparatus. 


ANATOMY  OF  THE  COMMON  FROG.  471 

Slit  open  the  skin  along  the  median  ventral  line  the 
whole  length  of  the  animal,  turn  the  skin  back,  and  then 
cut  through  the  muscular  walls  of  the  abdomen,  being  care- 
ful not  to  injure  the  underlying  organs.  The  viscera  will 
then  be  exposed  :  the  coiled  intestine,  the  large  liver,  and  in 
the  female  the  sexual  organs  at  either  side  ;  finally,  pos- 
teriorly, the  thin-walled  bladder,  B.  The  next  step  is  to 
seize  the  posterior  end  of  the  sternum  with  a  pair  of  for- 
ceps, lift  it  up,  cut  the  fibres  which  run  from  its  under  sur- 
face, and  cut  with  a  pair  of  strong  scissors  along  both  sides 
of  the  sternum  and  around  its  anterior  end,  so  as  to  remove 
it  entirely.  Underneath  the  sternum  lies  a  thin-walled  bag, 
the  pericardium,  enclosing  the  heart.  On  either  side  are 
the  lungs. 

To  complete  the  preparation  dissect  out  the  intestine,  by 
cutting  through  the  mesentery  ;  follow  it  to  the  stomach, 
which  must*be  separated  from  the  oesophagus  and  drawn 
aside  together  with  the  intestine,  while  the  liver  must  be 
turned  over  to  the  right  of  the  animal.  The  pericardium 
must  be  cut  through  and  removed  without  injury  to  the 
heart ;  finally,  the  skin  must  be  removed  from  the  hind 
legs.  If  the  dissection  is  of  a  male,  it  will  then  appear  very 
much  as  in  the  figure. 

The  heart  is  conical  in  shape  ;  its  apex  points  backwards, 
and  is  formed,  by  a  single  chamber,  the  ventricle,  with  thick 
muscular  Avails,  from  which  springs  on  the  ventral  surface  a 
little  to  the  right  the  truncus  arteriosus  (Ao),  which  runs 
forward  and  divides  into  the  two  aortic  arches.  The  base  of 
the  heart  contains  two  chambers,  the  right  and  left  auricles, 
the  separation  of  which  is  not  marked  externally.  A  large 
vein  (  V)  passes  from  the  liver  to  the  back  of  the  heart,  and 
there  empties  into  a  thin-walled  sac,  the  sinus  venosus, 
which  also  receives  on  either  side  a  vein  from  above,  the 
vencB  cavcB  superiores.  The  vein  from  the  liver  receives  also 
the  genital  and  renal  veins,  and  is  then  called  the  vena  cava 
inferior.  As  the  heart  continues  to  beat  for  many  hours 
after  a  frog  has  been  killed,  if  a  fresh  specimen  is  taken  for 
dissection  the  rythmically  alternating  dilatations  and  con- 
tractions may  be  observed.  The  order  of  contraction  is, 


472  ZOOLOGY. 

1st,  the  sinus  venosus  ;  3d,  both  auricles ;  3d,  the  ventricle  ; 
4th,  the  truncus. 

In  front  of  and  below  the  heart  may  be  seen  the  trachea, 
easily  recognized  by  the  hard  rings  of  cartilage,  and  having 
the  larynx  just  in  front  of  the  aortic  arches  and  giving  off 
two  branches  posteriorly,  the  bronchi,  which  run  directly  to 
the  lungs.  The  trachea  overlies  the  oesophagus,  which  ter- 
minates in  the  stomach  (St).  On  either  side  of  the  trachea 
lies  a  thyroid  gland  (th). 

The  liver  (Li)  is  a  large  brown  mass,  composed  of  two 
lobes,  of  which  the  left  is  the  larger,  and  subdivided  into 
two.  Between  the  two  lobes  lies  a  small  greenish  sac,  the 
gall-bladder  (b).  The  liver  receives  a  large  vein  ( pv)  from 
the  kidneys  ;  this  is  the  portal  vein,  which  distributes  to  the 
liver  the  blood  which  has  already  once  passed  through  the 
capillaries  of  the  other  abdominal  viscera.  The  hepatic  vein 
takes  the  blood  from  the  liver  directly  to  the  heart. 

The  stomach  (St),  when  in  situ,  lies  on  the  left  side  of  the 
abdominal  cavity,  its  oesophageal  end  being  the  largest ;  it 
leads  directly  into  the  intestine,  which  is  of  uniform  width 
throughout,  but  terminates  in  the  dilated  rectum  (R),  which 
in  its  turn  opens  into  the  cloaca.  To  the  ventral  surface  of 
the  cloaca  is  appended  the  bladder  (B).  Imbedded  in  the 
mesentery  near  the  commencement  of  the  intestine  is  a  pale 
compact  mass,  the  pancreas,  not  represented  in  the  figure, 
and  a  little  farther  from  the  stomach  a  small  round  dark 
body,  the  spleen  (Sp). 

The  kidneys  (Ki)  are  two  elongated  deep  red  bodies,  upon 
which  lie  a  number  of  yellow  spots,  the  adrenal  glands. 
The  renal  ducts  arise  from  the  outer  and  anterior  portion  of 
the  kidneys  and  then  run  backwards  as  two  white  convoluted 
canals  (vd),  at  first  very  narrow,  then  widening,  and  end- 
ing with  a  dilatation  immediately  before  they  open  into  the 
cloaca.  These  ducts  serve  at  once  as  ureters  and  vasa  defer- 
entia.  In  front  of  the  kidneys  lie  a  pair  of  oval  yellow 
bodies,  the  testes  (Te).  The  female  has  both  ureter  and 
oviduct.  The  ovary  varies  greatly  in  size  and  appearance 
according  to  its  condition.  The  oviduct  is  a  very  long  con- 
voluted tube  running  from  the  pericardium  backwards  to 


ANATOMY  OF  THE  COMMON  FROG.  473 

the  cloaca,  where  it  opens  just  in  front  of  the  ureter.  At 
the  season  of  reproduction  the  oviduct  is  found  very  much 
distended  with  ova.  Its  anterior  end  has  a  ciliated  opening 
into  the  body-cavity.  In  the  neighborhood  of  the  sexual 
glands  lies  the  fat-body  (/). 

The  lungs  (lu)  are  two  large  sacs  with  very  elastic  walls, 
richly  supplied  with  blood-vessels.  These  vessels  spring 
from  the  pulmonary  artery.  From  each  division  of  the 
truncus  arteriosus  are  given  off  four  branches  (Fig.  433,  II). 
The  first  is  the  pulmonary  aorta  (Pa),  which  also  gives  off 
a  large  cutaneous  branch  ;  the  second,  the  true  aortic  arch 
(Ao),  which,  curving  backwards,  unites  with  its  fellow  just 
in  front  of  the  kidneys  and  below  the  spinal  column,  to  form 
the  descending  aorta  ;  the  third  (cr),  the  carotid  artery,  run- 
ning to  the  head,  and  bearing  at  its  origin  the  singular  caro- 
tid gland  (eg]  ;  the  fourth,  the  lingual  artery.  The  blood 
is  returned  from  the  lungs  by  two  veins,  which  empty  into 
the  left  auricle. 

The  space  of  the  lower  jaw  is  covered  over  by  a  thin  trans- 
verse muscle  (My),  the  mylohyoid.  On  either  side  behind 
the  posterior  edge  of  this  muscle  lies  a  croaking  bag  or  air- 
sac  (S).  In  the  mouth  are  to  be  observed,  1st,  the  mus- 
cular tongue,  attached  by  its  anterior  end  to  the  lower  jaw, 
and  forked  posteriorly  ;  2d,  the  openings  of  the  nasal  cavi- 
ties ;  3d,  the  recessus  Eustachii,  lying  further  back,  and 
leading  into  the  tympanic  cavity  ;  4th,  the  opening  of  the 
oesophagus  ;  and  5th,  the  slit-like  epiglottis. 

The  muscles  are  best  dissected  in  alcoholic  specimens. 
The  muscles  of  the  hind  limbs  are  as  follows  :  On  the  ven- 
tral surface,  the  cut  ends  of  the  recti  abdominis  (r.  ##.); 
on  the  ventral  surface,  1,  of  the  thigh,  outwardly  musculm 
vastus  internus  (mvi),  the  adductor  longus  (a),  the  sar- 
torius  (ms),  adductor  magnus  (a"),  rectus  internus  minor 
(ri")  ;  the  rectus  internus  major  (ri1) ;  a  small  part  of  the 
adductor  brevis  can  be  seen  close  to  the  pubis  between  the 
adductor  magnus  and  the  rectus  internus  major  ;  underneath 
the  rectus  internus  major  lies  the  long  and  the  semitendino- 
sus  with  two  -heads  ;  2,  of  the  leg  (crus)  gastrocnemius  (g), 
and  between  that  muscle  and  the  bone  the  tibialis  posticus ; 


ZOOLOGY. 


£. 


jer. 


FIG.  4 33.—  Anatomy  of  the  common  Frog. 


ANATOMY  OF  THE  COMMON  FROG.  475 

in  front  is  the  tibialis  anticus  (fa).  On  the  dorsal  surface 
of  the  thigh  (Fig.  433,  III)  the  glutmus  (gl),  the  pyriformis 
(p),  the  rectus  anticus  femorus  (ret,),  the  vastus  externus 
(ve),  the  biceps  (#),  the  semimembranosus  (sm),  lying  deep 
between  the  biceps  and  semimembranosus  are  seen  the 
femoral  vessels  and  sciatic  nerve  ;  the  rectus  anticus,  vastus 
interims  and  externus  are  known  collectively  as  the  triceps 
femoris ;  in  the  leg  the  gastrocnemius  (g)  and  peroncsus  (p). 

The  sympathetic  nerves  can  be  seen  as  two  cords,  one  on 
either  side  of  the  vertebral  column.  The  spinal  nerves  can 
be  seen  as  white  threads  on  the  dorsal  surface  of  the  body- 
cavity.  The  brain  (Fig.  373)  may  be  dissected  out  by  open- 
ing the  skull  from  above.  The  olfactory  lobes  of  frogs  and 
toads  are  fused  together,  but  separate  in  the  tailed  Batrachia. 
The  seventh,  eighth,  and  ninth  spinal  nerves  unite  to 
form  the  very  large  sciatic  trunk  ;  the  intercommunications 
of  these  nerves  form  the  lumbar  plexus ;  while  the  second 
and  third  spinal  nerves  form  the  brachial  plexus  from  which 
arises  the  brachial  nerve.  (C.  S.  Minot.) 

Certain  glands  in  the  skin  of  some  Batrachians  secrete  a 
corrosive,  or  as  in  the  European  Salamandra  maculosa,  a  nar- 
cotic poison,  which  is  poisonous  to  small  animals.  The 
toads  secrete  in  the  parotid  glands  a  bad-smelling  fluid, 
which  applied  to  tender  skins  produces  erysipelas.  Lacerda 
states  that  the  poison  of  the  Brazilian  Bufo  ictericus  is  a 
milky  humor  from  the  glands  on  the  sides  of  the  neck.  The 
action  of  the  poison  is  less  fatal  to  small  animals  than  that 
of  the  European  toad  ;  it  gives  a  slight  acid  reaction  and  is 
not  soluble  in  alcohol,  while  that  of  the  European  toad  is. 

Like  fishes,  the  Batrachians  assume  high  colors  during 
the  breeding  season.  The  males  of  the  newts  at  this  time 


Fig.  433.— Anatomy  of  common  Frog.  My,  mylohyoid ;  sr,  sternoradials ;  th, 
thyroid  ;  lu,  lungs  ;  /,  fat-body  ;  Te,  testis ;  St,  stomach  ;  Sp,  spleen  ;  R,  rectum  ; 
a,  adductor  longus;  mvi,  vastus  interims ;  ms,  sartorius;  n',  rectus  interims 
major;  ta,  tibialis  anticus  ;  g,  gastrocnemius;  ri",  rectus  internus  minor;  a",  ad- 
ductor mafnus  ;  rob.  rectus'  abdominalis ;  B,  bladder  ;  vd,  vas  deferens  ;  &,  gall- 
bladder; Ki,  kidney  ;  pv,  portal  vein  ;  Li,  liver  ;  F,  vena  cava  inferior  ;  Ao,  aorta  ; 
8,  vocal  sac-,  or  croaking-bag. 

II.  Origin  of  the  arterial  trunks.    /,  arteria  ingualis  ;  eg,  carotid  gland,  which  is 
merely  a  rete  mirabile  ;  cr,  carotid  artery  ;  Ao<  aortic  arch:  Pa,  pulmonary  artery. 

III.  Dorsal  view  of  muscles  of  hind  leg.   ql,  glntseiw  ;  ra,  rectus  anterior  ;  p,  pyri- 
formis ;  ve,  vastus  externus ;  sm,  semi-menibranosus  ;  b,  biceps  ;  g,  gastrocneraius  ; 
per,  peronreus.— Drawn  by  C.  S.  Minot. 


476  ZOOLOGY. 

acquire  the  dorsal  crest  and  a  broader  tail-fin,  while  in  some 
species  prehensile  claws  are  temporarily  developed  on  the  fore 
legs  of  the  male.  The  males  of  the  Anura  (toads  and  frogs) 
are  musical,  the  females  being  comparatively  silent ;  the  vocal 
organs  of  the  male  are  more  developed  than  in  the  females,  and 
in  the  edible  frog  (Rana  esculenta)  large  sacs  for  producing 
a  greater  volume  of  sound  stand  out  on  each  side  of  the  head 
of  the  males.  Among  the  few  viviparous  Batrachians  known 
is  an  Alpine  European  Salamandra  (8.  atra)  which  brings 
forth  its  young  alive. 

It  is  common  to  find  tadpoles  in  the  winter  in  ponds, 
which  have  been  retarded  in  their  metamorphosis,  and  by 
artificial  means  this  retardation  may  be  greatly  increased. 
For  example,  "Wyman  is  said  to  have  kept  tadpoles  of  the 
bull-frog  for  seven  years  in  a  cellar. 

Unlike  the  higher  Vertebrates  the  segmentation  of  the  egg 
in  the  Amphibia  is  total,  the  process  beginning  usually  about 
three  hours  after  impregnation  in  the  frog,  and  lasting  twen- 
ty-four hours.  The  primitive  streak,  the  notochord  and 
nervous  system  then  arise  as  in  other  craniated  Vertebrates. 
After  the  appearance  of  the  branchial  arches,  the  gills  begin 
to  bud  out  from  them,  finally  forming  the  larger  gills  of  the 
tadpole.  Unlike  young  fishes,  the  yolk  is  entirely  absorbed 
before  the  tadpole  leaves  the  egg.  In  warm  climates  the 
tadpoles  hatch  in  four  or  five  days  after  the  eggs  are  laid. 
When  hatched  the  tadpole  is  not  so  well  developed  as  in  most 
young  fishes.  The  digestive  canal  at  first  is  simple  and 
straight.  Afterwards  it  becomes  remarkably  long  and  coiled 
in  a  close  spiral.  The  mouth  is  small  (Fig.  434,  A),  with  no 
tongue  and  only  horny  toothless  jaws.  The  vertebrae  of  the 
tadpole  are  biconcave  as  in  fishes,  afterwards  becoming  con- 
verted into  cup-and-ball  joints. 

The  accompanying  figures  represent  the  external  changes 
of  the  toad  from  the  time  it  is  hatched  until  the  form  of  the 
adult  is  attained.  The  tadpoles  of  our  American  toad  are 
smaller  and  blacker  in  all  stages  of  growth  than  those  of  the 
frog.  The  tadpole  is  at  first  without  any  limbs  (Fig.  434  A), 
and  with  two  pairs  of  gills ;  soon  the  hinder  legs  bud  out. 
After  this  stage  (B)  is  reached,  the  body  begins  to  diminish  in 


METAMORPHOSIS  OF  BATRACHIANS.  477 

size.  The  next  important  change  is  the  growth  of  the  front 
legs  and  the  partial  disappearance  of  the  tail  (C),  while  very 
small  toads  (D  and  E),  during  midsummer,  may  be  found  on 
the  edges  of  the  pools  in  which  some  of  the  nearly  tailless  tad- 
poles may  be  seen  swimming  about.  It  is  three  years  before 
the  Amphibia  are  capable  of  breeding.  In  the  newts  (Tri- 
ton) the  gills  are  in  three  pairs,  larger  and  more  complex 
than  in  the  frog  ;  the  fore  limbs  are  the  first  to  grow  out, 
and  the  gills  persist  long  after  the  hind  limbs  are  developed. 
In  the  newts  we  have  the  larval  state  of  the  toads  and  frogs 
persistent ;  thus  the  successive  steps  in  the  development  of 
the  individual  frog  is  an  epitome  of  the  evolution  of  the 
typical  forms  of  the  class  to  which  it  belongs. 


Fig.  434.— Metamorphosis  of  the  Toad.— After  Owen  ;  from  Tenney's  Zoology. 

In  certain  Batrachians  as  the  Alpine  salamander,  the  Su- 
rinam toad  (Pipa)  and  the  Hylodes  of  Guadaloupe  in  the 
West  Indies,  the  metamorphosis  is  suppressed,  development 
being  direct ;  though  the  young  have  gills,  they  do  not  lead 
an  aquatic  life.  In  the  axolotl  there  is  a  premature  devel- 
opment of  the  reproductive  organs,  the  larvae  as  well  as  the 
adults  laying  fertile  eggs. 

The  Batrachians  are  inhabitants  of  the  warmer  and  tem- 
perate zones.  Frogs  extend  into  the  arctic  circle.  The 
Aniblystoma  mavortium  breeds  at  an  altitude  of  about  8000 
feet  in  the  Rocky  Mountains.  Rana  septentrionalis  Baird 
extends  to  Okak,  Northern  Labrador,  where  the  climate  is  as 
extreme  as  that  of  Southern  Greenland  ;  frogs  have  also  been 


478  ZOOLOGY. 

observed  at  the  Yukon  Kiver  in  lat.  60°  N.,  but  the  climate 
there  is  milder  than  that  of  Labrador.  The  common  toad 
and  a  salamander  (Plethodon  glutinosa  Baird  ?)  extend  to 
Southern  Labrador. 

Nearly  700  species  of  existing  Batrachians  are  known,  101 
of  which  are  North  American,  and  about  100  fossil  forms 
have  been  described. 

There  are  five  orders  of  Batrachians,  Professor  Cope's 
classification  being  adopted  in  this  work.  Those  Batrachians 
with  persistent  gills  are  sometimes  called  Perennibranchiates. 

Order  1.  Trachystomata. — The  sirens  have  a  long  eel-like 
body,  with  persistent  gills  ;  there  is  no  pelvis  or  hind  limbs, 
and  the  weak,  small  fore  legs  are  four  or  three-toed.  The 
great  siren,  Siren  lacertina  Linn.,  is  sometimes  a  metre  in 
length,  and  has  four  toes  in  the  fore  leg  ;  it  lives  in  swamps 
and  bayous  from  North  Carolina  and  Southern  Illinois  to 
the  Gulf  of  Mexico.  A  small  siren  with  three  toes  and 
small  gills  is  Pseudobranclms  striatus  Le  Conte.  It  occurs 
in  Georgia. 

Order  2.  Proteida. — This  group  is  represented  by  the 
Proteus  of  Austrian  caves  and  the  mud-puppy  (Necturus) 
of  the  United  States.  These  Batrachians  have  bushy  gills, 
with  gill-openings  and  well-developed  teeth.  In  Proteus, 
which  is  blind,  there  are  three  toes  in  the  fore  feet  and  two 
in  the  hinder  pair.  In  the  mud-puppy,  Necturus  (formerly 
Menobranchus)  lateralis  Baird,  each  foot  is  four-toed.  The 
head  and  body  are  broad  and  flat,  brown  with  darker  spots. 
It  has  small  eyes  and  is  about  half  a  metre  (from  8  inches  to 
2  feet)  in  length.  It  inhabits  the  Mississippi  Valley,  extend- 
ing eastward  into  the  lakes  of  Central  New  York.  The 
Proteus  as  well  as  the  mud-puppy  lay  eggs. 

Order  3.  Urodela. — The  tailed  Batrachians  or  Salaman- 
ders rarely  have  persistent  gills,  these  organs  being  larval  or 
transitory  ;  the  body  is  still  long  and  fish-like,  the  tail  some- 
times with  a  caudal  fin-like  expansion  as  in  the  newts,  but  is 
usually  rounded,  and  the  four  legs  are  always  present.  With 
only  one  or  two  viviparous  exceptions,  most  of  them  lay  eggs 
in  the  water.  The  eggs  of  Triton  are  laid  singly  on  sub- 
merged leaves  ;  those  of  Notophthalmus  viridescens  are  laid 


SALAMANDERS.  479 

singly  on  leaves  of  Myriophyllum,  which  adhere  to  the  glu- 
tinous egg,  concealing  it.  (Cope.)  Those  of  Desmognathus 
are  laid  connected  by  a  thread  both  on  land  and  in  water. 
The  common  land  salamander,  or  Plethodon  erytlironotum 
Baird,  lays  its  eggs  in  summer  in  packets  under  damp 
stones,  leaves,  etc.  ;  the  young  are  born  with  gills,  as  is  the 
case  with  the  viviparous  Salamandra  atra  of  the  Alps.  The 
possession  of  gills  by  land  salamanders,  which  have  no  use 
for  them,  and  which  consequently  drop  off  in  a  few  days, 
leads  us  justly  to  infer  that  the  land  salamanders  are  the  de- 
scendants of  those  which  had  aquatic  larvae. 

The  lowest  form  of  this  order  is  the  aquatic  Congo-snake 
or  Ampliiuma  means  Linn.,  in  which  the  body  is  large,  very 
long,  round  and  slender,  with  small  rudimentary  two-toed 
limbs  ;  there  are  no  gills,  though  spiracles  survive.  It  lives 
in  swamps  and  sluggish  streams  of  the  Southern  States. 

A  step  higher  in  the  Urodelous  scale  is  the  Menopoma,  which 
is  still  aquatic,  with  persistent  gills,  but  the  body  and  feet 
are  as  in  the  true  salamanders.  The  Menopoma  Alleghani- 
ense  Harlan,  called  the  hellbender  or  big  water  lizard,  is 
about  half  a  metre  (1^-2  feet)  in  length,  and  inhabits  the 
Mississippi  Valley.  Allied  to  the  Amphiuma  is  the  gigantic 
Japanese  salamander,  Cryptobranchus  Japonicus  Van  der 
Hoeven,  which  is  a  metre  in  length.  Allied  in  size  to  this 
form  was  the  great  fossil  salamander  of  the  German  Tertiary 
formation,  Andrias  Scheuchzeri,  the  homo  diluvii  testis  of 
Scheuchzer,  thought  by  this  author  to  be  a  fossil  man. 

In  the  true  salamanders  the  body  is  still  tailed,  the  eyes  are 
rather  large  ;  there  are  no  spiracles  ;  they  breathe  exclusively 
by  their  lungs,  except  what  respiration  is  carried  on  by  the 
skin. 

The  genus  AmUystoma  comprises  our  largest  salamanders  ; 
they  are  terrestrial  when  adult,  living  in  damp  places  and 
feeding  on  insects.  The  larvae  retain  their  gills  to  a  period 
when  they  are  as  large  or  even  larger  than  the  parent.  The 
most  interesting  of  all  the  salamanders  is  the  AmUystoma 
mavortium,  whose  larva  is  called  the  axolotl,  and  was  origi- 
nally described  as  a  perennibranchiate  amphibian  under  the 
name  of  Siredon  lichenoides  Baird.  This  larva  is  larger  than 


480  ZOOLOGY. 

the  adult,  terrestrial  form,  sometimes  being  about  a  third  of 
a  metre  (12  inches)  in  length,  the  adult  being  twenty  centim- 
etres (8  inches)  long,  forming  an  example  of  what  occurs 
in  the  Amphibians  and  also  certain  insects,  of  the  excess  in 
size  and  bulk  of  the  larva  over  the  more  condensed  adult 
form.  This  law  is  also  strikingly  observed  in  the  Pseudes 
(Fig.  437).  This  fact  of  prematuritive,  accelerated,  vegetative 
development  of  the  larva  over  the  adult  is  an  epitome  of  what 
has  happened  in  the  life  of  this  and  other  classes  of  animals. 

The  fossil,  earliest 
representatives  of  the 
Amphibians,  as  we 
shall  see  farther  on, 
were  enormous,  mon- 
strous, larval,  prem- 
ature forms  corn- 
Fig.  435.— Siredon  or  larval  Salamander.— From  pared  With  their  de- 

Tenney's  zoology.  scendants.    The  same 

law  holds  good  in  certain  groups  of  Crustacea  (trilobites), 
insects,  fishes,  reptiles  and  mammals. 

The  axolotl  or  siredon  abounds  in  the  lakes  of  the  Eocky 
Mountain  plateau  from  Montana  to  Mexico,  from  an  altitude 
of  4000  to  8000  or  9000  feet ;  the  Mexican  axolotl  being  of 
a  different  species,  though  closely  allied  to  that  of  Colorado, 
Utah  and  Wyoming.  The  Mexicans  use  the  animal  as  food. 
Late  in  the  summer  the  siredons  at  Como  Lake,  Wyoming, 
where  we  have  observed  them,  transform  in  large  numbers 
into  the  adult  stage,  leaving  the  water  and  hiding  under 
sticks,  etc.,  on  land.  Still  larger  numbers  remain  in  the 
lake,  and  breed  there,  as  I  have  received  the  eggs  from  Mr. 
William  Carlin,  of  Como.  Thousands  of  the  fully-grown 
siredons  are  washed  ashore  in  the  spring  when  the  ice  melts. 
They  do  not  appear  at  the  surface  of  the  lake  until  the  last 
of  June,  and  disappear  out  of  sight  early  in  September. 
The  eggs  are  laid  in  musses,  and  are  2  millimetres  in  diameter. 
Mr.  F.  F.  Hubbell  has  observed  in  Como  Lake,  July  23d, 
young  siredons  four  to  six  centimetres  (1£- 2-J  inches)  in 
length,  and  September  3d  specimens  eight  centimetres  (3 
inches)  long.  In  Utah,  Mr.  J.  L.  Barfoot  raised  in  1875 


HABITS  OF  THE  AXOLOTL.  481 

several  adults  from  the  larva,  and  I  have  been  told  that  sire- 
dons  in  the  mountains  among  the  miners'  camps  near  Salt 
Lake  City  leave  the  water  and  transform.  It  thus  appears 
that  in  the  elevated  plateaus*  as  well  as  at  the  sea-coast,  some 
siredons  transform  while  others  do  not.  Mexican  siredons 
have  for  a  number  of  years  been  bred  from  eggs  in  the 
aquaria  of  Europe,  laying  eggs  the  second  year. 

The  change  from  the  larva  to  the  adult  consists,  as  we  have 
observed,  in  the  absorption  of  the  gills,  which  disappear  in 
about  four  days  ;  meanwhile  the  tail-fins  begin  to  be  absorbed, 
the  costal  grooves  become  marked,  the  head  grows  smaller, 
the  eyes  larger,  more  protuberant,  and  the  third  day  after 
the  gills  begin  to  be  absorbed  the  creature  becomes  dark, 
spotted,  and  very  active  and  restless,  leaving  the  water.  Their 
metamorphosis  may  be  greatly  retarded  and  possibly  wholly 
checked  by  keeping  them  in  deep  water.  The  internal 
changes  in  the  bones  of  the  head  and  in  the  teeth  are  very 
marked,  according  to  Dumeril. 

Experiments  made  in  Europe  show  that  the  legs  and  tail 
of  the  axolotl,  as  of  other  larval  salamanders,  may  be  repro- 
duced. We  cut  oif  a  leg  of  an  axolotl  the  first  of  November  ; 
it  was  fully  reproduced,  though  of  smaller  size  than  the 
others,  a  month  later.  The  tail,  according  to  Mr.  L.  A. 
Lee,  if  partly  removed,  will  grow  out  again  as  perfect  as  ever, 
vertebrae  and  all. 

The  Tritons  or  water-newts,  represented  by  our  common, 
pretty  spotted  newt,  Diemyctylm  viridescens  Kafinesque,  are 
also  known  in  Europe  to  become  sexually  mature  in  the  larval 
state  when  the  gills  are  still  present,  as  has  been  observed  by 
three  different  naturalists.  The  female  larva  of  Lissotriton 
punctatus  has  been  known  to  lay  eggs. 

Order  4.  Gymnophiona. — The  blind  snake  with  its  several 
allies  is  the  representative  of  this  small  but  interesting  order. 

*  It  has  been  stated  by  De  Saussure,  Cope,  Marsh,  and  more  recently 
by  Weistnann,  that  the  siredon  does  not  change  in  its  native  elevated 
home.  No  naturalist  has  seen  the  Mexican  siredon  transform  into  an 
Amblystoma,  but  as  it  does  so  in  abundance  in  Wyoming  and  Utah, 
it  probably  transforms  in  Mexico.  (The  adult  Mexican  form  has  recent- 
ly been  found,  and  is  at  the  Smithsonian  Institution.) 


482  ZOOLOG  Y. 

The  body  is  snake-like,  being  long  and  cylindrical ;  there 
are  no  feet  and  no  tail,  the  vent  being  situated  at  the  blunt 
end  of  the  body.  The  skin  is  smooth  externally,  with  scales 
embedded  in  it,  but  with  scale-like  transverse  wrinkles.  The 
eyes  are  minute,  covered  by  the  skin.  The  species  inhabit 
the  tropics  of  South  America,  Java,  Ceylon,  and  live  like 
earthworms  in  holes  in  the  damp  earth,  feeding  on  insect 
larvae.  They  are  large,  growing  several  feet  in  length. 
Cecilia  lumbricoides  Daudin  inhabits  South  America.  Cos- 
cilia  compressicauda  of  Surinam  is  viviparous,  the  young 
being  born  in  water  and  possessing  external  gills  which  are 
leaf-shaped  sacs  resting  against  the  sides  of  the  body  ;  when 
the  animal  leaves  the  water  they  are  absorbed,  leaving  a  scar. 
(Peters.)  Siphonops  Mexicana  Dumeril  and  Bibron,  is  a 
Mexican  form. 

Order  5.  Stegocepliala. — Here  belong  an  order  of  extinct 
Batrachians,  with  three  suborders,  Labyrintliodontia,  Gano- 
cephala,  and  Microsauria  (Cope).  In  these  forms  the  skulls 
were  either  somewhat  like  those  of  the  frogs,  or  the  crania 
were  roofed  in  by  solid  flat  bones,  similar  to  those  of  ganoid 
fishes.  The  vertebrae  were  biconcave.  The  limbs  of  the 
Labyrinthodonts  were  like  those  of  the  tailed  Batrachians,  of 
small  size  and  weak,  compared  with  the  great  size  of  the 
body.  Von  Meyer  states  that  Arcliegosaurus  possessed 
branchial  arches  when  young,  and  that  probably  other  Laby- 
rinthodonts resembled  it  in  this  respect.  It  had  paddles 
instead  of  feet,  the  head  had  an  armor  of  plates,  and  the 
body  was  covered  with  overlapping  ganoid  scales.  It  had 
teeth  like  those  of  ganoid  fishes  ;  it  had  a  notochord,  the 
bodies  of  the  vertebrae  being  neither  bony  nor  cartilaginous. 
Owen  regards  it  as  combining  the  characters  of  the  perenni- 
branchiate  Amphibians  and  the  Ganoid  fishes.  It  was  a 
little  over  a  metre  (3£  feet)  in  length.  It  is  a  representative 
of  the  suborder  Ganocephala. 

While  the  older  text-books  in  the  restorations  of  Lctby- 
rinthodon  represented  it  as  like  a  toad,  with  large  legs  and 
tailess,  it  is  now  known  that  some  of  the  gigantic  prede- 
cessors of  the  salamanders  and  tritons  had  long  tails,  while 
others  had  long,  cylindrical,  snake-like  bodies.  Unlike  exist- 


LABYRINTHODONT  BATRACHIANS.  483 

ing  Batrachians,  their  fossil  ancestors  had  an  armor  of  large 
breast-plates,  with  smaller  scales  on  the  under  and  hinder 
part  of  the  body. 

But  the  largest  forms  were  the  true  Labyrinthodonts  repre- 
sented in  the  Carboniferous  rocks  of  this  country  by  Baplietes, 
and  in  Europe  by  Anthracosaurus,  Zygosaurus,  and  in  the 
Permian  beds  of  Texas  by  Eryops.  Labyrinthodonts  also 
abounded  in  the  Triassic  Period,  and  forms  like  the  Euro- 
pean Ldbyrintliodon  or  M astodontosaurus  must  have  been 
colossal  in  size.  Footprints  occur  in  the  Subcarboniferous 
rocks  of  this  country  which  indicate  forms  still  larger  than 
any  yet  discovered  in  the  Old  World.  A  large  number 
(thirty -four  species,  referable  to  seventeen  genera)  of  medium- 
sized  Labyrinthodonts  have  been  described  from  the  coal 
measures  of  Ohio  by  Cope  which  were  characterized  by 
their  long,  limbless,  snake-like  bodies  and  pointed  heads, 
forming  a  still  more  decided  approach  to  the  Ganoids.  This 
was  the  lowest  group  of  Stegocephala,  called  Microsauria  by 
Dawson. 

Thus  we  have  in  these  Labyrinthodonts  synthetic  or  an- 
nectant  forms,  which  connect  the  fishes  with  the  Am- 
phibians, and  on  the  other  hand  point  to  the  incoming  of 
the  reptiles.  They  were  thus  prematuritive,  larval  forms, 
which  in  certain  characters  anticipated  the  coming  of  a 
higher  type  of  Vertebrate.  The  reptiles  were  ushered 
in  during  the  Permian  Period,  the  rocks  of  this  age  imme- 
diately overlying  the  coal  measures,  though  it  should  be 
stated  that  there  are  obscure  traces  of  reptiles  in  the  Carbon- 
iferous rocks.  It  is  not  improbable  that  evidence  will  be 
found  to  substantiate  the  impression  that  the  reptiles, 
together  with  but  independently  of  the  Amphibians, 
branched  off  from  the  Ganoid  fishes,  or  from  extinct  forms 
related  to  them. 

Order  6.  Anurc,. — The  toads  and  frogs  represent  this 
order,  which  comprises  tailless  Batrachians,  with  the  four 
limbs  present,  the  toes  being  very  long  (due  to  the  great 
length  of  the  calcaneus  and  astragalus),  while  the  body  is 
short  and  broad,  the  skin  soft  and  smooth,  scaleless,  though 
small  plates  are  sometimes  embedded  in  it.  The  lower  jaw  is 


484  ZOOLOGY. 

usually  toothless.  The  larvae  are  called  tadpoles,  and  repre- 
sent the  adult  form  of  the  Perennibranchiates.  The  exter- 
nal gills  are  in  the  adult  replaced  by  shorter  internal  ones. 

Among  the  lower  frogs  or  arciferous  Anura  of  Cope,  i.e., 
those  with  the  acromial  and  corocoid  bones  divergent  and 
connected  by  distinct  cartilage  plates,  are  certain  forms, 
as  Alytes,  Pelobates,  and  Pelodytes,  whose  breeding  habits 
are  peculiar  and  interesting.  The  eggs  of  Pelodytes  are 
deposited  in  small  clusters  in  the  w-ater,  those  of  Pelo- 
bates  in  a  thick  loop.  The  male  of  the  European  Alytes 
obstetricans  winds  a  string  of  eggs  which  it  takes  from 
the  female,  and  goes  into  the  water,  where  it  remains 
until  the  young  (which  have  no  gills)  are  hatched.  The 
American  Scaphiopus,  or  spade-footed  toad,  is  not  known  to 
have  this  obstetrical  habit.  This  singular  toad  appears  sud- 
denly and  in  great  numbers.  It  remains  but  a  day  or 
two  in  the  water,  where  it  lays  its  eggs  in  bunches  from 
one  to  three  inches  in  diameter.  The  tadpoles  hatch 
in  about  six  days  after  the  eggs  are  laid ;  their  growth  is 
rapid,  the  young  toads  leaving  the  water  in  two  or  three 
weeks.  The  croaking  of  this  toad  is  harsh,  peculiar,  and 
need  not  be  confounded  with  that  of  any  other  species. 
(Putnam.)  As  the  spc-de-footed  toads  are  rarely  seen,  it  is 
possible  that  they  burrow  in  the  soil,  like  the  European 
Alytes.  Another  peculiarity  in  the  reproductive  habits  of 
Alytes,  Pelobates,  Cultripes,  and  Pelodytes  is  that  they 
spawn  at  two  seasons  instead  of  one,  and  that  their  larvae, 
like  Pseudes  (Fig.  437),  attain  a  greater  size  than  those  of 
other  frogs  before  completing  their  metamorphosis.  (Cope.) 

Among  the  tree-toads,  Polypedates  of  tropical  Western 
Africa,  contrary  to  the  usual  habits  of  frogs,  deposits  its  eggs 
in  a  mass  of  jelly  attached  to  the  leaves  of  trees  which  bor- 
der the  shore  overhanging  a  pond.  On  the  arrival  of  the 
rainy  season,  the  eggs  become  washed  into  the  pond  below, 
where  the  male  frog  fertilizes  them.  Our  common  piping 
tree-toad  (Hyla  Pickeringii  Le  Conte),  about  the  middle  of 
April,  in  the  neighborhood  of  Boston,  attaches  her  eggs 
simply  to  aquatic  plants.  The  young  are  hatched  in  about 
twelve  days. 


SUPPRESSED  METAMORPHOSIS. 


485 


As  an  example  of  -a  suppressed  metamorphosis,  due  ap- 
parently to  a  radical  difference  in  the  physical  environment 
of  the  animal,,  may  be  cited  the  case  of  a  tree-toad  in  the 
island  of  Guadaloupe.  There  are  no  marshes  on  this  island, 
consequently  in  a  species  of  Hylodes  the  development  of 
the  young  is  direct  ;  they  hatch  from  the  eggs  which  are 
laid  under  moist  leaves,  without  tails,  and  are  otherwise,  ex- 
cept in  size,  like  the  adults.  On  the  other  hand,  a  tree-toad 
of  the  island  of  Martinique  (Hylodes  Martinicensis,  Fig. 
436)  has  tadpoles,  which  it  carries  on  its  back.  The  female 
of  Nototrema  marsupiatum  Dumeril  and  Bibron,  of  the 
Andes,  has  a  marsupium  or  sac  on  its  back  in  which  the 
young  are  carried.  The  Notodelphys 
of  South  America  has  similar  habits  ; 
for  example,  the  female  Opisthodel- 
pliys  (Notodelpliys)  ovifera  has  a  dor- 
sal sac  a  centimetre  deep  in  which 
the  eggs  are  carried.  In  the  young 
of  this  and  of  Gastrotheca  also  of 
Central  America,  Peters  found  traces 
of  external  gills.  The  Pipa,  or  Suri- 
nam toad  (Pipa  Americana  Laurent), 
which  has  no  tongue,  neither  teeth  in 
the  upper  jaw,  has  similar  breeding 
habits.  In  this  interesting  toad  the 
young,  according  to  Prof.  Wyman, 

are  provided  with  small  gills,  which,  however,  are  of  no 
use  to  them,  as  the  tadpoles  do  not  enter  the  water,  but  are 
carried  about  in  cavities  on  the  back.  The  eggs  are  placed 
by  the  male  on  the  back  of  the  female,  where  they  are 
fertilized.  The  female  then  enters  the  water  ;  the  skin 
thickens,  rises  up  around  each  egg  and  forms  a  marsupial 
sac  or  cell.  The  young  pass  through  their  metamorphosis 
in  the  sacs,  having  tails  and  rudimentary  gills  ;  these  are 
absorbed  before  they  leave  their  cells,  the  limbs  develop, 
and  the  young  pass  out  in  the  form  of  the  adult. 

The  toad  (Bufo  Untiginosus  Shaw)  is  exceedingly  useful  as 
a  destroyer  of  noxious  insects.  It  is  nocturnal  in  its  habits  ; 
is  harmless,  and  can  be  taken  up  with  impunity,  though  it 


Fig.  436._Thc 


Martinique 
e  young 


480 


ZOOLOGY. 


Fig.  437.— The  Paradoxical  Frog.  1,  2,  larva,  nearly  of  natural  size  ;  3,  4,  Pseudea 
min-uta,  natural  size.— 1,  2,  after  Pizarro  ;  3,  4,  after  Garman.— From  the  American 
Naturalist. 


CLASSIFICATION  OF  BATRACHIANS.  487 

gives  out  an  irritant  acrid  fluid  from  the  skin,  which  may 
poison  the  eyelids.  In  New  England  toads  begin  to  make 
their  peculiar  low  trilling  notes  from  the  middle  to  the  20th 
of  April ;  from  the  latter  date  until  the  first  of  June  they 
lay  their  eggs  in  long  double  strings,  and  the  tadpoles  (Fig. 
434)  are  usually  hatched  in  about  ten  days  after  the  eggs  are 
deposited.  (Putnam.) 

The  paradoxical  frog  of  South  America  (Pseudes  para- 
doxa  "Wagler,  Fig.  437, 1,  2,  the  larva)  is  remarkable  from  the 
fact  that  the  larva  is  larger  than  the  adult.  3  and  4  repre- 
sent another  species  of  Pseudes  (P.  minuta). 

The  highest  genus  of  the  Anura  is  Rana,  of  which  there 
are  numerous  species,  our  American,  forms  being  the  bull- 
frog (Rana  pipiens  Linn. ),  the  Rana  palustris  Le  Conte,  or 
pickerel -frog,  and  the  marsh-frog  (Rana  lialecina  Kalm). 
They  lay  their  eggs  in  masses  in  the  water  in  April,  May, 
and  the  early  part  of  June,  according  to  the  latitude. 

While  most  frogs  are  eaten  by  birds,  and  in  such  cases  are 
preserved  from  extinction  by  their  nocturnal  habits  and  their 
protective  resemblance  to  the  herbage  and  the  bark  and  leaves 
of  trees,  Thomas  Belt  records  the  case  of  a  little  Nicaraguan 
frog  which  is  very  abundant  in  damp  woods,  and  "hops 
about  in  the  daytime,  dressed  in  a  bright  livery  of  red  and 
blue."  Its  immunity  from  destruction  is  due  to  the  fact 
that  ducks  and  fowl  could  not  be  induced  to  eat  it,  owing  to 
its  unpleasant  taste,  the  same  reason  inducing  birds  to  reject 
certain  bright-colored  caterpillars,  which  are  distasteful  to 
them. 


CLASS  IV.— BATRACHIA.. 

Amphibious  Vertebrates,  with  gills  in  certain  adult  aquatic  forms,  all 
breathing  air  by  lungs  ;  the  skin  of  existing  species  naked;  with  true 
limbs  like  those  of  higher  Vertebrates  ;  skull  with  two  occipital  condyles  ; 
heart  with  two  auricles  and  one  ventricle.  Mostly  oviparous  ;  a  distinct 
metamorphosis. 

Order  1.   Trachystomata. — Body  long,  eel-like,  with  persistent  gills ; 
no  pelvic  bones  or  hind  limbs ;  no  maxillary  bone.     (Siren.) 


488  ZOOLOGY. 

Order  2.  Proteida.—  Body  flattened,  with  persistent  gills,  and  gill- 
openings  ;  a  maxillary  bone.  (Proteus,  Necturus.) 

Order  3.  Urodela. — No  persistent  gills,  body  with  a  tail  ;  no  gill-open- 
ings except  in  Menopoma  and  Amphiuma.  (Salamandra.) 

Order  4.  GymnopMona. — Body  snake-like,  no  feet ;  no  tail ;  young  with 
gill-opeuings,  but  no  gills.  (Coecilia.) 

Order  5.  Stegocephala. — Extinct  forms  ;  the  temples  with  a  bony  roof; 
often  large ;  either  snake-like,  without  limbs,  or  with  pad- 
dle-like limbs,  or  with  four  legs  ;  teeth  with  or  without 
labyrinthine  structure.  (Archegosaurus,  Labyrinthodon.) 

Order  6.  Anura. — Body  short,  tailless,  with  four  limbs  ;  toes  very  long  ; 
leapers  ;  larvae  tailed.  (Bufo,  Rana.) 

Laboratory  Work. — The  student  should  carefully  follow,  with  a  speci- 
men in  hand,  the  description  of  the  structure  of  the  frog,  aided  by  the 
figure  ;  then  should  make  a  skeleton  of  the  same  species.  These 
studies  should  then  be  followed  by  a  close  comparison  with  the  struc- 
ture of  a  mud-puppy  and  of  a  salamander — the  osteology  and  anat- 
omy of  the  softer  parts  receiving  equal  attention.  The  breeding  hab- 
its of  the  Batrachians  may  be  studied  by  confining  them  in  jars  or 
aquaria.  The  embryology  can  best  be  studied  by  hardened  stained 
sections  of  the  eggs. 


CLASS  V.— EEPTILIA  (Lizards.  Snakes,  Turtles,  and 
Crocodiles). 

General  Characters  of  Reptiles. — In  the  members  of  the 
present  class  we  have  a  still  farther  elaboration  of  a  type  of 
structure  which  first  appears  in  the  Batrachians,  with  the 
addition  of  features,  which  on  the  other  hand  are  wrought 
out  in  a  more  detailed  manner  in  the  birds,  so  much  so  that 
while  the  fishes  and  Batrachians  form  one  series  (Ictliyop- 
sida),  a  study  of  different  fossil  reptiles,  especially  the  bird- 
like  reptiles  (Dinosaurs  and  Pterosaurs),  which  clearly  con- 
nect the  birds  with  the  reptiles,  shows  that  the  two  latter 
groups  should  be  united  into  a  series  called  Sauropsida. 
Thus  no  one  class  of  Vertebrates  stands  alone  by  itself  ;  every 
year  fresh  researches  by  palaeontologists,  and  the  re-examina- 
tions of  living  Vertebrates,  especially  as  to  their  embryonic 
history,  proves  that  no  single  class,  not  even  a  type  so  well 


REPTILES.  489 

circumscribed  as  the  modern  birds,  is  without  links  forming 
genetic  bonds  allying  them  all  together.  In  fact,  the  different 
classes  of  Vertebrates,  as  well  as  of  other  branches  of  the 
animal  kingdom,  form  an  ascending  series,  from  the  more 
generalized,  though  not  always  simple  forms  (numerous 
groups  comprising  synthetic  types),  to  those  which  are  more 
specialized,  i.e.,  in  which  separate  organs  or  groups  of  or- 
gans are  elaborated  and  worked  out  in  great  detail.  This  is 
the  tendency  all  through  nature,  and  were  Cuvier  himself 
now  living,  and  were  he  to  examine  the  facts  revealed  since 
his  death,  he  would,  as  many  others  in  advanced  life  have 
done,  cast  aside  the  limited,  analytical  notions  of  the  past, 
based  as  they  were  on  fragmentary  evidence,  and  adopt 
the  more  philosophical  principles  of  classification,  based  on 
sciences  that  were  in  embryo  thirty  or  forty  years  since. 
These  reflections  have  great  force  in  the  study  of  a  class  like 
the  reptiles  where  there  are  a  larger  number  (five)  of  extinct, 
than  of  living  (four)  orders,  and  where  the  fossil  types  were 
of  a  more  general,  almost  embryonic  type,  and  consequently 
gigantic  and  ill-shapen,  showing  a  tendency  to  extremes  or 
prematurity  in  development  rather  than  to  an  equality  in  and 
maturity  of  the  whole  organization  compared  with  their  de- 
scendants. A  high  degree  of  specialization  of  type  tends 
nearly  always  in  living  beings,  plants  as  well  as  animals,  to  a 
condensation  and  higher  grade  of  form.  These  animals  also 
have  given  a  name  to  the  Age  of  Reptiles,  the  middle  or 
Mesozoic  age  of  the  world,  when  they  were  the  dominant  type 
of  life. 

The  essential  characters  of  reptiles  are  the  following  :  As 
regards  the  skeleton,  the  bodies  of  the  vertebrae  vary  in  being 
either  biconcave,  concave  in  front,  concave  behind,  or  flat 
at  each  end  ;  the  cup-and-ball  vertebrae  are  most  common, 
forming  a  strong  and  flexible  joint  well  fitted  for  general 
motion.  The  ribs  are  well  developed,  the  sternum  is  rhom- 
boidal ;  there  are  usually,  if  not  always,  more  than  three 
toes.  The  body  is  covered  with  scales  ;  the  blood  is  cold,  the 
heart  has  in  the  crocodiles,  the  highest  order,  four  chambers  ; 
two  or  more  aortic  branches  persist,  and  certain  membranes, 
called  an  amnion  and  allantois,  envelop  the  embryo. 


490 


ZOOLOGY. 


The  vertebral  column  is  now  more  distinctly  marked  off 
than  in  the  Batrachians  ;  a  cervical  and  lumbar  region  being 
indicated  in  most  reptiles  except  the  snakes  and  turtles.  Well- 
marked  ribs  exist  in  nearly  all  the  vertebrae  of  the  trunk, 
except  in  the  turtles,  where  the  so-called  ribs  are  possibly, 

B 

f\   \          r\  ' 


Fig.  438.—  Skull  of  a  Tur- 
tle seen  from  behind,  1, 
basi  occipital  ;  2,  exoocipi- 
ital  ;  5,  basi- 
rootic  (pe- 


tal  ;  3,  supraoccipital  ;  5,  basi- 
sphenoid  ;  15,  prootic  (pe- 
trosal)  ;  17,  quadrate.  —  After 
Gegeubaur. 


according  to  Gegenbaur,  modified 
transverse  processes. 

The  skull  of  reptiles  is  much 
more  like  that  of  birds  than  of 
Amphibians.  There  is  a  single 
occipital  condyle,  and  the  lower 
jaw  is  articulated  by  the  quad- 
rate-bone to  the  base  of  the  skull. 
The  primitive  skull,  or  that  part 
immediately  enclosing  the  brain, 
has  an  incomplete  roof,  but  still 
is  more  bony  than  in  Batrachi- 
ans ;  while  owing  to  the  great 
size  of  the  bones  developed  orig- 
inally in  and  from  the  palato- 
quadrate  cartilage,  but  a  small 

part    Of   the    true    Skull    is    to    be 

seen. 

hyoid  suspensorium  in  fishes  (hyomandibular  and  symplectic 

bones)  are,  as  in  the  Batrachians,  entirely  separate  from  the 

skull. 

While  the  limbs  are,  as  a  rule,  absent  in  the  snakes,  the 
fore  legs  always  wanting,  in  a  few  forms,  as  the  pythons, 


Cupper,  «,  lower  pieces  of  the  tar- 
_.,  .  ,        sus  ;  m,  metatarsus  ;  /-  y,  metatarsa- 

The  parts  forming   the   Ha  of  the  toes. 


STRUCTURE  OF  REPTILES.  491 

boas,  and  Tortrices,  the  pelvis  exists  in  a  rudimentary  state, 
and  attached  to  it  is  a  pair  of  rudimentary  hind  legs  ending 
in  claws  ;  in  all  other  existing  reptiles  the  limbs  are  directly 
comparable  with  those  of  birds  and  mammals,  the  bones  of 
the  legs  being  best  developed  in  the  Chelonians  (turtles), 
which  have  nine  carpal  bones  and  five  fingers  in  each  foot. 
Certain  extinct  saurians  had  paddle-like  limbs,  others  bird- 
like  limbs,  and  still  others  approached  the  crocodilian  type, 
in  which  the  carpal  bones  and  phalanges  become  reduced  in 
number.  In  the  hind  limbs  an  intermedium  (in  birds  only 
present  in  the  embryo)  is  united  with  the  tibiale  bone  to 
form  an  astragalus  or  heel-bone. 

The  scales  of  reptiles  are  very  characteristic,  though  scales 
existed  on  the  underside  of  the  body  of  most  Stegocephalous 
Batrachia.  The  scales  of  lizards  and  snakes  are  developed 
from  the  cutis.  The  large  horny  plates  of  Chelonians  are 
greatly  developed  and  unite  above  with  the  "ribs"  to  form 
the  shell  or  carapace,  while  nine  large  plates  below  form 
the  plastron. 

The  teeth  are  simple,  conical,  and  while  in  the  lizards 
and  snakes  they  may  exist  on  the  palatine  and  pterygoid 
bones,  in  the  crocodiles,  where  they  are  implanted  in  sockets 
of  the  jaw-bones,  they  are,  as  in  the  mammals,  confined  to 
the  maxillary  bones.  They  are  reproduced  as  fast  as  they 
are  shed.  The  Chelonians  have  no  teeth,  the  jaws  being,  as 
in  birds,  enclosed  in  a  stout  horny  case,  developed  from  the 
epidermis.  There  is  a  middle  and  internal  ear  much  as  in 
birds.  The  New  Zealand  lizard,  Hatteria,  is  the  only  reptile 
which  has  the  beginning  of  a  spiral  turn  indicated  in  its 
cochlea,  which  in  other  reptiles  is,  as  in  birds,  merely  a 
flask-shaped  cavity.  (Rolleston.)  The  eyes  of  reptiles  ap- 
proach those  of  birds,  and  in  both  there  is  an  upper  and  a 
lower  movable  eyelid  besides  a  nictitating  membrane. 

True  nostrils  exist  in  reptiles  for  the  first  time  among 
Vertebrates. 

The  tongue  is  either  not  extended  out  of  the  mouth,  and 
is  broad,  as  in  turtles  and  crocodiles  and  some  lizards,  or  as 
in  most  lizards  and  all  snakes  it  is  long,  slender,  forked,  and 
can  be  darted  rapidly  out  of  the  mouth. 


492  ZOOLOGY. 

True  lips  now,  as  in  birds,  border  the  jaw-bones,  while 
salivary  glands  for  the  first  time  in  the  Vertebrates  appear 
in  the  Chelonians  and  lizards  ;  besides  these  there  are  smaller 
glands  in  the  lips  of  lizards  and  snakes,  the  poison-glands 
of  the  rattlesnake,  viper,  etc.,  being  modifications  of  these 
labial  glands. 

While  the  oasophagiis  is  wide  and  the  stomach  usually 
quite  simple,  in  the  crocodiles  there  is  a  muscular  gizzard 
approaching  that  of  birds,  and  there  is  a  special  pyloric  por- 
tion in  the  crocodiles  like  that  of  grallatorial  and  swimming 
birds.  The  liver  and  pancreas  have,  as  in  birds,  two  or  more 
excretory  ducts,  and  a  gall-bladder  is  always  present.  A 
large  fat-body  (Fig.  440, /)  is  present  on  each  side  of  the 
body. 

The  lungs,  trachea,  and  larynx  of  reptiles  are  much 
simpler  than  in  birds  ;  in  the  long  slender-ringed  trachea 
there  is  an  approach  to  that  of  birds,  but  the  lungs  are 
modelled  on  the  Amphibian  type  ;  the  larynx,  especially  in 
the  Chelonians  and  crocodiles,  is  much  more  perfect  than  in 
the  Amphibians. 

The  organs  of  circulation  show  a  decided  advance  in  situ- 
ation over  the  Batrachians.  The  heart  (Fig.  440)  recedes 
farther  back  into  the  thorax.  Of  the  two  auricles  the  right 

o 

and  larger  one  receives  the  systemic  and  the  left  the  pul- 
monary veins.  In  all  but  the  crocodile  the  ventricle  has 
a  partition,  the  right  half  containing  venous  and  the  left 
arterial  blood,  while  in  the  crocodiles  there  are  two  ven- 
tricles, so  that  the  heart  is  four-chambered.  In  the  lizards 
two  aortic  branches  (a  right  and  a  left)  survive.  In  the 
crocodiles  a  vessel  which  gives  off  the  right  aortic  arch  and 
the  carotids  arises  from  the  left  ventricle,  while  a  left  aortic 
arch  and  the  pulmonary  arteries  arise  from  the  right  ven- 
tricle. In  the  reptiles  as  in  birds  there  are  two  superior  as 
well  as  one  inferior  vena  cava.  In  reptiles  as  in  lower  Ver- 
tebrates there  are  no  true  lymphatic  glands  ;  an  organ  re- 
sembling them  is  present  in  reptiles  (Fig.  440,  th),  forming  a 
small  swelling  situated  behind  the  angle  of  the  lower  jaw. 

While  the  brain  is  still  simple,  though  it  fills  the  cavity  of 
the  skull,  the  different  lobes  being  subequal  in  size,  the  cere- 


ANATOMY  OF  THE  LIZARD. 


493 


Fig.  440. — Anatomy  of  a  lizard,  Sceleporus  undulatus.  t,  trachea  { <?,  carotid  artery; 
th,  thyroid  gland  ;  ft,  ventricle  of  the  heart— above  are  the  two  auricles ;  lu,  lung ; 
/,  liver  turned  out;  #,  stomach  ;  i,  intestine  ;  a,  vent  — above  it  the  cloaca  is  laid 
open  to  disclose  the  openings  (o  o)  of  the  kidneys  (&);  above  are  the  two  openings  of 
the  oviducts ;  n,  oviduct ;  o,  ovary  ;  »,  vena  cava  ;  /,  fat-body.— Drawn  by  A.  F. 
Gray  from  dissections  made  by  the  author. 


494  ZOOLOGY. 

belluin  is  small,  especially  in  the  serpents.  In  the  croco- 
diles the  brain  most  approaches  that  of  birds,  the  cerebellum 
being  larger  than  usual  in  the  middle,  and  in  this  respect 
somewhat  approaching  the  birds.  Corpora  striata  (which 
are  thickenings  of  the  outer  walls  of  the  cerebral  hemispheres) 
and  the  anterior  commissure  of  the  cerebral  hemispheres  are 
present  for  the  first  time  in  the  vertebrate  series, 

The  kidneys  (Fig.  440,  k)  are  lobulated,  varying  in  foim 
and  position,  and  usually  situated  near  the  cloaca,  the  ureters 
being  short  and  opening  into  the  cloaca.  The  reproductive 
organs  are  generally  liko  those  of  the  B;itrachians.  The 
ovaries  lie  on  each  side  of  the  vertebral  column,  and  vary  in 
size  with  the  season,  being  largest  during  the  time  of  repro- 
duction. The  oviducts  (Fig.  440,  n)  are  voluminous  coiled 
canals,  which  in  most  reptiles  open  into  the  cloaca ;  in  the 
turtles,  however,  opening  into  the  "neck  of  the  so-called 
urinary  bladder.  After  the  egg  passes  into  the  oviduct  it 
is  enveloped  by  the  "  white"  or  albumen,  which  is  secreted 
in  the  anterior  part  of  the  oviduct,  while  the  thick-walled 
terminal  part  secretes  the  shell. 

The  external  differences  between  the  sexes  is  more  marked 
than  in  the  Amphibians.  According  to  Darwin,  the  sexes  of 
the  Chelonians  and  snakes  differ  very  slightly  ;  male  rattle- 
snakes are  said  to  be  more  yellow ;  in  the  East  Indian  Dip- 
sas  cynodon  the  male  is  bright  green,  while  the  female  is 
bronze-colored.  Male  lizards  are  usually  larger,  while  male 
snakes  are  always  smaller  than  those  of  the  opposite  sex. 
Various  appendages,  such  as  crests,  warts,  horns,  etc.,  when 
present  in  both  sexes,  are  most  developed  in  the  males, 
while  the  colors  and  markings  are  brighter  in  the  latter  sex. 

The  moulting  of  the  skin  is  effected  by  its  being  pushed  off 
by  the  upward  growth  of  fine,  temporary  cuticular  hairs. 
On  certain  parts  of  the  body,  as  on  the  underside  of  the 
capsular  skin  and  scales  of  the  eyes,  these  hairs  do  not  de- 
velop. After  the  skin  is  loosened,  it  dries  and  is  readily 
shuffled  off. 

The  eggs  of  turtles,  like  those  of  birds, .are  very  large, 
the  yolk  mass  being  greatly  developed.  The  lizards,  snakes, 
and  crocodiles  lay  their  eggs  in  sand  or  light  soil,  while  those 


DEVELOPMENT  OF  REPTILES.  495 

of  the  iguana  are  laid  in  the  hollows  of  trees.  Certain 
snakes,  as  the  vipers,  are  viviparous.  In  many  snakes  and 
lizards  the  development  of  the  embryo  goes  on  in  the  egg 
before  it  leaves  the  oviduct ;  such  species  are  said  to  be  ovo- 
viviparous,  the  young  being  born  living.  The  Eutcenia 
sirtalis,  or  common  striped  snake,  brings  forth  its  young 
alive,  and  is  probably  ovoviviparous  rather  than  viviparous. 

The  early  phases  of  the  development  of  the  reptiles,  in- 
cluding the  origin  of  the  amnion  and  allantois,  is  much  as 
in  the  chick.  In  the  turtle,  by  the  time  that  the  heart  has 
become  three -chambered,  the  vertebrae  have  reached  the 
root  of  the  tail,  the  eyes  have  become  entirely  enclosed  in 
complete  orbits,  and  the  allantois  begins  to  grow.  The 
nostrils  may  now  be  recognized  as  two  simple  indentations 
at  the  end  of  the  head,  and  at  first  are  not  in  communica- 
tion with  the  mouth,  but  soon  a  shallow  furrow  leads  to  it. 
The  shield  begins  to  develop  by  a  budding  out  laterally  of 
the  musculo-cutaneous  layer  along  the  sides  of  the  body, 
and  by  the  growth  of  narrow  ribs  extending  to  the  edge  of 
the  shield.  In  the  oviparous  snakes  (e.g.,  Natrix  torquata) 
the  embryo  partially  develops  before  the  egg  is  laid,  while 
the  young  hatches  in  two  months  after  the  egg  is  deposited. 
By  this  time  the  amnion  is  perfected,  the  head  is  distinct, 
and  shows  the  eyeball  and  ear-sac  ;  also  the  maxillary  and 
mandibular  processes.  The  allantois  is  about  as  large  as  the 
head.  The  long  trunk  of  the  serpent  grows  in  a  series  of 
decreasing  spirals,  and  when  live  or  six  are  formed,  the  rudi- 
ments of  the  liver  and  the  primordial  kidneys  are  discern- 
ible. At  the  latter  third  of  embryonic  life  the  right  lung 
appears  as  a  mere  appendage  to  the  beginning  of  the  left. 

The  reptiles  are  essentially  tropical  and  subtropical  ani- 
mals ;  they  are  scarce  in  north  temperate  countries,  though 
in  North  America  snakes  extend  north  farther  than  lizards  ; 
in  Europe  snakes  cease  at  60°  north  latitude,  and  at  6000 
feet  elevation  in  the  Alps  ;  lizards  in  Europe  sometimes  ex- 
tend farther  north  than  snakes,  and  ascend  to  an  elevation 
of  10,000  feet  in  the  Alps.  Reptiles  are  usually  wanting  in 
oceanic  islands  which  possess  no  indigenous  mammals,  though 
lizards  are  sometimes  found  on  islands  where  there  are 


496  ZOOLOGY. 

neither  mammals  nor  snakes.  The  reptiles  in  cool  climates 
hibernate,  while  those  of  the  tropics  have  a  summer-sleep  in 
the  dry  season,  becoming  active  when  the  rainy  season  begins. 

There  are  about  three  thousand  species  of  living  reptiles 
known,  of  which  three  hundred  and  fifty-eight  are  North 
American ;  between  three  and  four  hundred  fossil  forms 
have  been  described.  The  reptiles  are  divided  into  nine 
orders,  of  which  five  are  extinct. 

Order  I.  Opliidia.  The  snakes,  of  which  there  are  over 
one  hundred  and  thirty  species  in  America  north  of  Mexico, 
have  a  remarkably  long  cylindrical  body,  the  tail  very  long 
and  slender ;  they  are  footless,  with  no  shoulder  girdle,  and 
are  covered  with  scales,  which  are  all  shed  simultaneously. 
These  scales  are  epidermal  growths,  and  while  usually  they 
overlap,  in  a  few«cases  (Acroehordus,  etc.)  they  are  tubercu- 
lar, and  do  not  overlap.  The  eyes  are  not  protected  by  true 
lids,  but  the  latter  are  thin,  covering  the  eye  permanently, 
thus  accounting  for  the  fixed,  stony  stare  of  snakes.  The 
number  of  vertebrae  (wliich  are  hollow  in  front  and  convex 
behind),  may  in  the  boa  amount  to  more  than  four  hundred. 
Each  vertebra,  except  the  first  (the  atlas)  is  provided  with 
ribs,  and  the  processes  with  articular  facets,  which  interlock- 
ing give  great  strength  and  flexibility  to  the  spinal  column. 
The  hyoid  bone  is  very  slightly  developed,  though  the 
tongue  is  long,  forked,  can  be  rapidly  darted  out,  and  with- 
drawn into  a  sheath  ;  the  quadrate  bones  connecting  the 
lower  jaw  with  the  skull  are  movable.  The  bones  of  the 
brain-case  are  firmly  united  together,  while  those  of  the  jaws 
and  palate  are  more  or  less  freely  movable  to  allow  the  snake 
(the  boa  especially)  to  distend  its  throat  immensely  and 
swallow  comparatively  large  animals,  though  ordinary  snakes 
will  swallow  large  toads  and  frogs  and  other  snakes  but 
slightly  smaller  than  themselves.  In  order  to  retain  the 
prey  and  prevent  its  slipping  out  of  the  mouth,  the  recurved 
short  conical  teeth  are  developed  on  the  maxillary,  palatine, 
pterygoid,  and  mandibular  bones,  and  occasionally  on  the 
premaxillaries  ;  they  are  not  set  in  sockets,  and  consequently 
are  not  used  to  crush  or  tear  food. 

The  peculiar  gliding  motion  of  snakes  is  effected  by  the 


ANATOMY  OF  THE  SNAKE.  497 

movements  of  the  large  ventral  scales,  which  are  successively 
advanced,  the  hinder  edges  of  the  scales  resting  on  the 
ground  and  forming  fulcra ;  resting  on  these  the  body  is 
then  drawn  or  pushed  rapidly  forwards. 

The  brain  of  serpents  is  small,  much  as  in  the  lizards,  the 
cerebellum  being  especially  small  and  flat,  while  the  cerebral 
hemispheres  together  form  a  mass  broader  than  long. 

The  more  characteristic  features  of  the  internal  anatomy 
of  snakes  is  a  want  of  symmetry  in  the  paired  organs,  as  seen 
in  the  absence  of  a  second  functional  lung,  and  second  pul- 
monary artery,  one  of  the  lungs  being  minute,  rudimentary, 
while  the  other  is  very  long  and  large  ;  the  trachea  is  also 
very  long,  while  the  right  ovary  is  larger  than  the  left  and 
placed  in  front  of  it.  The  other  viscera  are  so  arranged  as  to 
pack  well  in  the  long  nairow  body-cavity. 

The  student  should  dissect  a  snake  with  the  aid  of  the  ac- 
companying figure  of  the  common  striped  snake  (Eutcenia 
sir  tails  Baird). 

A  few  snakes  are  viviparous,  as  the  vipers  ;  others  are  ovo- 
viviparous.  In  the  oviparous  Natrix  torquata  of  Europe, 
the  embryo  partly  develops  before  the  egg  is  laid,  Avhile  the 
young  hatches  in  two  months  after  the  egg  is  deposited.  At  this 
time  the  amnion  is  fully  formed,  the  head  is  distinct,  as  well 
as  the  eyeball,  and  ear  sac.  The  long  body  grows  in  a  series 
of  decreasing  spirals,  and  when  five  or  six  are  formed,  the 
rudiments  of  the  liver  and  of  the  primordial  kidneys  may  be 
detected,  while  at  the  latter  third  of  embryonic  life,  the 
right  lung  appears  as  a  mere  appendage  to  the  beginning  of 
the  left.  The  embryo,  at  the  time  of  hatching,  is  provided 
with  a  temporary  horny  tooth  on  the  snout  to  cut  through 
the  egg  shell. 

Most  snakes  conform  in  coloration  to  the  nature  of  the 
soil  or  places  they  frequent ;  some  being,  as  in  the  rattlesnake 
of  the  western  plains,  of  the  color  of  the  soil  in  which  they 
burrow  ;  the  little  green  snake  is  of  the  color  of  the  grass 
through  which  it  glides  ;  other  are  dull  gray  or  dusky,  har- 
monizing with  the  color  of  the  trunks  of  trees  on  which 
they  rest.  The  poisonous  Elaps  of  the  Central  American 
orest  is  gaily  and  conspicuously  colored  ;  indeed  it  can  af- 
ford to  be  brightly  colored,  as  no  birds  dare  to  attack  it. 


Pig.  441.— Anatomy  of  the  common  striped  Snake.  Hy,  hyoidean  apparatus  ;  TV, 
trachea  ;  (h,  thyroid  ;  Oe,  oesophagus  ;  T,  thymus  ;  Iff.  heart ;  Br,  bronchus  ;  L, 
lung;  A,  air-gac;  Li,  liver;  Ov,  ovary ;  Sp,  spleen;  Pa.  pancreas:  Od,  oviduct; 
Cl.  cloaca  ;  R.  rectum  :  Od',  right  oviduct  cut  off;  «,  ureU  r  ;  K.  kidnev  ;  F,  vena 
;  /.  Intertine.— Drawn  bv  V  S  Miuot 


POISONOUS  SNAKES. 


499 


The  Salenoglyph  poisonous  snakes  may  always  be  recog- 
nized by  their  broad,  flattened  heads,  and  usually  short  thick 
bodies.  The  poison  gland  of  the  rattlesnake  (Fig.  442,  a)  is 
a  modified  salivary  gland.  The  two  fangs  are  modifications 
of  maxillary  teeth,  each  of  which  has  been,  so  to  speak, 
pressed  flat,  with  the  edges  bent  towards  each  other,  and 
soldered  together,  so  as  to  form  a  hollow  cylinder  open  at 
both  ends,  the  poison  duct  leading  into  the  basal  opening. 
When  the  fangs  strike  into  the  flesh,  the  muscles  closing 
the  jaws  press  upon  the  poison  gland,  forcing  the  poison 
into  the  wound.  The  poison-fangs  are  largest  in  the  most 
deadly  species,  as 
the  yiper  ( Vipera), 
the  puff  adder 
(Clotho),  the  rat- 
tlesnake, and  fer- 
de-lance  (Trigono- 
cephalus),  but  are 
small  in  the  asps 
or  hooded  snakes 
(Naja).  The  bite 
of  the  rattlesnake 
is  intensely  painful; 
it  is  best  cured  by 
sucking,  freely  Ian- 


Fio.  442.  —  Head  of  the  rattlesnake  :   «  «,  poison  gland 
and  its  excretory  duct  :  e,  anterior  temporal  muscle  ;  /, 
posterior  temporal  muscle  ;    </,  digastricus  ;    A,  external 
-.  i  pterygoid  muscle  ;  i,  middle  temporal  muscle  ;  q,  arti- 

Cing,  and  by  Cautei'-    calo-nuudllary  ligament  which   joins   the  aponeurotic 
T      capsule  of  the  poison  gland  ;   ?%  the  cervical  angular 
WOUnd,    muscle  ;  t.  vertebro-mandibular  muscle  ;  u,  costo-  man- 

dibular  muscle- 


,-1 
IZing     tne 

and  drinking  large 
quantities  (at  least  a  pint)  of  whiskey  or  brandy,  sufficient 
ordinarily  to  produce  insensibility.  Deaths  from  the  bite  of 
rattlesnakes  are  not  common,  while  in  India  it  is  estimated 
that  several  thousand  people  annually  die  from  the  bite  of 
the  cobra  —  10,000  dying  each  year  from  the  bite  of  snakes 
and  the  attacks  of  wild  beasts.  The  "rattle"  of-  the  rattle- 
snake is  a  horny  appendage  formed  of  buttonlike  compart- 
ments ;  the  sound  made  by  the  rattle,  which  has  been  com- 
pared by  some  to  the  stridulation  of  a  Carolina  locust,  or  of 
the  Cicada,  is  an  alarm  note,  warning  the  intruder  ;  the  rat- 
tle is  sprung  before  the  snake  strikes.  Allied  to  this  snake 


500  ZOOLOGY. 

is  the  copperhead  (Ancistrodon  confer 'trix  Linn.)  and  the 
black  mocassin  (Ancistrodon  piscivorus  Linn. ).  In  the  water 
snakes  the  tails  are  laterally  compressed,  while  the  poison- 
fangs  are  small.  These  snakes  are  not  much  over  a  metre  in 
length,  and  live  far  from  land  in  the  East  Indian  seas. 

The  poisonous  snakes  stand  lowest  in  the  series  ;  they  are 
succeeded  by  the  striped  snake,  milk  adder,  and  by  the  boas, 
which  attain  a  length  of  five  metres  ;  while  the  anaconda 
grows  eight  metres  long. 

In  time  snakes  reach  back  to  the  Eocene  Tertiary  period, 
when  a  great  sea-snake  (Titanophis),  represented  by  several 
species,  one  six  metres  in  length,  haunted  the  coast  of  New 
Jersey,  while  in  the  western  lake-deposits  of  the  same  age, 
forms  allied  to  the  existing  boa-constrictor  were  not  un- 
common. The  snakes,  then,  appear  to  be  a  modern  type 
compared  with  the  lizards,  turtles,  and  crocodiles. 

Order  2.  PythonomorpJia. — This  group  includes  a  num- 
ber of  colossal  serpent-like  forms,  with  paddle-like  feet,  which 
are  regarded  by  Cope  as  the  types  of  a  distinct  order,  char- 
acterized by  a  complex  suspensorium,  by  the  absence  of  a 
sternum  and  sacrum,  by  the  rootless  teeth,  recurved  parie- 
tal bones,  etc. 

They  were  fifty  and  sixty  feet  in  length,  and  Mosasaurus 
maximus  Cope,  from  New  Jersey  was  still  more  colossal. 
They  combined  characters  of  the  snakes,  lizards,  and  plesio- 
saurs,  and  correspond  in  a  degree  to  the  descriptions  of  the 
mythical  sea-serpent. 

The  resemblance  to  the  Ophidians  is  still  farther  strength- 
ened by  the  late  discovery  by  Professor  F.  H.  Snow,  that  one 
of  the  forms  (Liodori)  was  covered  above  by  small  imbricated 
scales,  like  those  of  the  snakes,  rather  than  large  ones,  like 
those  of  reptiles.  The  more  abundant  type  is  the  Mosa- 
saurus of  the  Cretaceous  seas,  which  was  a  huge  sea-serpent 
originally  referred  by  Cuvier  and  Owen  to  the  neighborhood 
of  the  lace-lizards  ( VaranidcB) ;  Cope  describes  it  as  a  long 
slender  reptile,  with  a  pair  of  powerful  paddles  in  front,  a 
moderately  long  neck,  and  flat  pointed  head,  with  a  long 
forked  tongue.  The  very  long  tail  was  flat  and  deep,  like 
that  of  a  great  eel,  forming  a  powerful  propeller.  The 


ORDER  OF  LIZARDS.  501 

arches  of  the  vertebral  column  interlocked  more  extensively 
than  in  other  reptiles  except  the  snakes.  They  swam  rapidly 
through  the  water  by  rapid  undulations  of  their  bodies  aided 
by  the  paddles.  The  skull  was  not  so  strong,  though  as 
light  as  that  of  the  serpents.  ' '  While  the  jaws  were  longer,  the 
gape  was  not  so  extensive  as  in  serpents  of  the  higher  groups, 
for  the  os  quadratum,  the  suspensor  of  the  lower  jaw,  though 
equally  movable  and  fastened  to  widely  spread  supports,  was 
much  shorter  than  in  them.  But  there  was  a  remarkable 
arrangement  to  obviate  any  inconvenience  arising  from  these 
points.  While  the  branches  of  the  under  jaw  had  no  natural 
connection,  and  possessed  independent  motion,  as  in  all  ser- 
pents, they  had  the  additional  peculiarity,  not  known  else- 
where among  Vertebrates  (except  with  snakes),  of  a  movable 
articulation  a  little  behind  the  middle  of  each.  Its  direction 
being  oblique,  the  flexure  was  outwards  and  a  little  down- 
wards, greatly  expanding  the  width  of  the  space  between 
them,  and  allowing  their  tips  to  close  a  little.  A  loose  flexi- 
ble pouch-like  throat  could  then  receive  the  entire  prey 
swallowed  between  the  branches  of  the  jaw  ;  the  necessity  of 
holding  it  long  in  the  teeth,  or  of  passing  it  between  the 
short  quadrate  bones  could  not  exist.  Of  course  the  glottis 
and  tongue  would  be  forwards. "  The  order  became  extinct 
before  the  Tertiary  Period. 

Order  3.  Lacertilia.  —The  existing  lizards  or  Saurians  are 
tho  survivors  or  descendants  of  a  multitude  of  forms,  many 
colossal  in  size,  which  characterized  the  Permian  and  Meso- 
zoic  periods  ;  while  the  extinct  forms  of  reptiles  were  in 
many  cases  synthetic  types,  with  affinities  to  fishes,  Am- 
phibians, and  even  birds.  The  group  as  now  existing  is  well 
circumscribed. 

Most  lizards  have  cylindrical  bodies,  usually  covered  with 
small  overlapping  scales,  with  a  long,  slender  tail,  and  general- 
ly two  pairs  of  feet,  the  toes  long  and  slender,  and  ending  in 
claws.  They  run  with  great  rapidity,  and  are  active,  agile 
creatures,  adorned  with  bright  metallic  colors,  in  some  cases 
green  or  brown,  simulating  the  tints  of  the  vegetation  or 
soil  on  which  they  live  ;  some  are  capable  of  changing  their 
color  at  will,  as  in  the  chameleon  and  Anolis ;  this  is  due  to 


502  ZOOLOGY. 

the  fact  that  the  pigment  cells  or  chromatophores  are  under 
the  influence  of  the  voluntary  nerves. 

While  the  scales  of  the  body  are  developed,  as  a  rule,  from 
the  epidermis,  in  the  scink  there  are  dermal  scales  (scutes), 
and  such  dermal  plates  in  the  head  may  unite  with  the  bones 
of  the  skull.  In  most  lizards,  all  except  the  Geckos,  the 
vertebra?  are  procoelous,  i.e.,  with  a  ball-and-socket  joint, 
the  vertebrae  being  rounded  in  front,  and  concave  behind. 
In  the  Geckos  the  vertebral  column  is  fish-like,  the  notochord 
persisting  except  in  the  centre  of  each  vertebra,  which  is  bi- 
concave. In  many  lizards  (Lacerta,  Iguana  and  the  Geckos), 
the  middle  of  each  caudal  vertebra  has  a  thin  cartilaginous 
partition,  and  it  is  afc  this  point  that  the  tails  of  these  liz- 
ards break  off  so  easily  when  seized.  In  such  cases  the  tail 
is  renewed,  but  is  more  stumpy.  The  tail  of  the  specimen 
of  Sceloporus  (Fig.  440)  which  we  dissected  is  much  shorter 
than  in  the  normal  animal,  and  must  have  grown  out  after 
having  been  lost. 

The  throat  is  often  distensible  by  the  hyoid  apparatus  ; 
but  the  bones  of  the  jaws  are  firm,  the  bones  united  in  front. 
Both  jaws  are  provided  with  teeth,  while  some  have  them 
developed  on  the  palatine  and  pterygoid  bones.  The  teeth 
are  usually  simple,  sharp,  conical,  as  in  most  lizards,  includ- 
ing the  Monitor,  or  they  are  flattened,  blade-like,  with  ser- 
rated edges,  as  in  the  Iguana,  or  as  in  Cyclodus  they  are 
broad,  adapted  for  crushing  the  food.  Most  lizards  prey  on 
insects  ;  some  live  on  plants.  New  teeth  are  usually  devel- 
oped at  the  bases  of  the  old  ones.  They  are  attached  to  the 
surface  of  its  jaws ;  in  certain  extinct  forms  (Thecodonts) 
they  are  lodged  in  sockets.  (Huxley.)  The  eyelids  are 
well  developed  except  in  the  Geckos,  in  which  the  lids  are 
modified  somewhat,  as  in  the  snakes,  to  form  a  transparent 
skin  over  the  cornea  of  the  eyes.  The  tongue  is  free  and 
long,  sometimes  forked  ;  in  the  iguana  it  ends  in  a  horny 
point. 

While  the  limbs  are  usually  present,  one  or  the  other  pair 
may  in  rare  cases  (in  Pseudopus  the  fore  feet  are  wanting  ;  in 
Chirotes  the  hind  feet  are  absent)  be  absent,  or  as  in  Am- 
pliisbmna  and  its  allies  the  feet  are  entirely  wanting,  though 


HORNED   TOADS.  503 

the  shoulder-girdle  invariably  remains,  the  pelvic-girdle  in 
such  cases  disappearing ;  the  pelvis  being  complete,  how- 
ever, when  the  hind  limbs  are  present.  The  feet  are  five- 
toed.  The  internal  anatomy  of  lizards  has  already  been  de- 
scribed and  illustrated  on  p.  493.  In  the  snake-like  lizards 
(Anguis)  the  left  lung  is  the  smaller,  and  in  Acontias 
and  Typhline  it  is  almost  wanting.  A  urinary  bladder, 
wanting  in  the  snakes,  is  present  in  lizards. 

The  lizard  lays  eggs  in  the  sand  or  soil ;  those  of  the  iguana 
are  deposited  in  the  hollows  of  trees.  Certain  lizards  are 
viviparous. 

There  are  between  seven  hundred  and  eight  hundred  species 
of  existing  lizards,  most  of  which  inhabit  tropical  or  subtrop- 
ical countries  ;  eighty-two  species  of  lizards  inhabit  America 
north  of  Mexico.  The  earliest  lizards  date  back  to  the  Kim- 
meridge  or  middle  division  of  the  Jurassic  rocks. 

Reviewing  some  of  the  more  interesting  lizards  in  the  as- 
cending order,  we  may,  passing  over  the  snake-like,  limbless 
Ampliisbmna,  and  the  limbless  glass  snake  (Opheosaurus), 
first  consider  the  chameleon  of  the  Mediterranean  shores,  in 
which  the  eyes  are  movable  with  a  circular  eyelid,  and  with 
the  five  toes  in  two  opposable  groups  adapted  for  grasping 
twigs  of  trees.  It  is  remarkable  for  its  power  of  changing 
its  colors.  The  tongue  of  the  chameleon  (Fig.  443)  is 
capable  of  extending  five  or  six  inches,  and  is  covered  with 
a  sticky  secretion  for  the  capture  of  insects,  as  the  crea- 
ture itself  is  very  sluggish.  The  chameleon  of  our  country 
is  the  Anolis  of  the  Southern  States,  and  is  a  long  smooth- 
bodied  lizard,  which  can  change  its  color  from  a  bright  pea- 
green  to  a  deep  bronze-brown. 

The  horned  toads  (Phrynosoma)  are  characteristic  of  the 
dry  western  plains  ;  the  body  is  broad,  flattened,  and  armed 
with  spines  ;  its  coloration  depends  on  that  of  the  soil  it  in- 
habits. It  will  stand  long  fasts.  When  Phrynosoma  Dou- 
glassii  of  the  Northwestern  Territories  and  States  is  about  to 
moult,  small  dry  vesicles  appear  on  the  back  and  sides,  run- 
ning along  the  horizontal  rows  of  pyramidal  scales  forming 
the  margin  of  the  abdomen.  In  a  day  or  two  the  vesicles 
break  and  desquamatioii  begins,  which  continues  for  eight  or 


504  ZOOLOGY. 

ten  days,  the  skin  finally  separating  from  the  spines  of  the 
head  and  the  claws.     (Hoffman.) 

Our  most  common  lizard  in  the  Middle  and  Southern 
States  is  Sceloporus  undulatus  Harlan  (Fig.  440).  It  is 
common,  running  up  trees.  The  iguanas  are  very  large  liz- 
ards inhabiting  the  West  Indies  and  Central  America ;  the 
head  is  protected  by  numerous  small  shields,  with  a  dorsal  row 
of  bristling  spines.  They  are  about  three  feet  long,  live  in 
the  lower  branches  of  trees,  and  are  said  to  be  excellent  eat- 
ing. A  still  larger  form,  closely  resembling  the  iguanas,  is 
the  sea-lizard  (Amblyrliynclms)  of  the  Galapagos  Islands, 
where  it  lives  in  the  rocks  by  the  shore,  feeding  on  seaweeds. 
These  large  creatures  are  among  the  largest  of  existing  liz- 


Fig.  443.— Tongue  of  Chameleon.    Natural  size.— After  Rymer  Jones. 

ards,  being  eighty-five  centimetres  (over  3  feet)  in  length. 
Closely  allied  to  the  iguanas  were  a  number  of  extinct  sau- 
rians  of  colossal  size  which  flourished  in  the  Jura-Trias  and 
Chalk  Periods. 

The  largest  lizard  in  Mexico  is  the  Heloderma  Jiorridum 
of  Wiegmann.  It  grows  to  the  length  of  one  metre  (over 
three  feet).  It  is  allied  to  the  iguanas,  but  the  body  is 
heavily  tuberculated.  Heloderma  suspectum  Cope,  inhab- 
its southern  Utah,  Arizona,  and  New  Mexico.  The  largest 
of  the  existing  lizards  are  the  monitors,  or  species  of  Vara- 
nus,  of  tropical  rivers,  which  nearly  rival  the  crocodiles  in 
size,  being  five  or  six  feet  in  length. 

Order  4.  Chelonia. — Although  the  tortoises  and  turtles 
are  a  well  circumscribed  group,  with  no  aberrant  or  connect- 


ANATOMY  OF  THE  TURTLE.  505 

ing  forms,  yet  they  have  some  affinities  with  the  Batrachia. 
They  are  distinguished  from  the  other  reptiles  by  the  shell, 
the  upper  part  forming  the  carapace,  and  the  lower  the 
plastron  ;  these  two  parts  unite  to  form  a  case  or  box  within 


Fig.  444. — Skeleton  of  European  Tortoise,  with  the  plastron  or  under  shell  removed. 
—After  Owen. 

which  the  turtle  can  retract  its  head  and  limbs  and  tail. 

Owing  to  the  presence  of  the  carapace,  the  dorsal  vertebrae 

are  immovable,  and  the  ribs  do  not  move  upon  the  vertebrae. 

The  bones  of  the  ventral  shield  or  plastron  are  usually 


506 


ZOOLOGY. 


nine  in  number.  The  jaws  are  toothless,  being,  as  in  birds, 
encased  in  horny  beaks  ;  there  are  rarely  fleshy  lips ;  the 
tongue  is  spoon-shaped  and  immovable.  The  heart  consists 
of  two  auricles  and  a  ventricle.  The  brain  has  larger  cere- 
bral lobes  than  in  the  lizards.  The  eyes  have  a  third  lid,  or 
nictitating  membrane.  The  student  can  best  obtain  an 
idea  of  the  organization  of  the  turtles  by  studying  the  skel- 
eton and  dissecting  a  turtle  with  the  aid  of  the  accompany- 
ing description  and  figure  of  the  common  turtle.  * 

The  common  swamp-turtle  (Chrysemy*  picta)  is  a  good 
type  of  the  Chelonia.  The  animal  is  enclosed  in  a  hard  shell 
made  up  of  an  arched  dorsal  portion,  and  a  flat  ventral  por- 


Pig.  445. — Ventral  epidermal  plates  of  Ghrysemys  picta. — Drawn  by  C.  S.  Minot. 

tion,  the  two  connected  laterally,  but  widely  separated  an- 
teriorly to  give  exit  to  the  head  and  fore  limbs,  and  pos- 
teriorly for  the  tail  and  hind  limbs.  These  parts  can  all  be 
withdrawn  within  the  protecting  shell,  by  being  doubled  or 
folded  back  upon  themselves.  The  soft  parts  of  the  skin  are 
covered  with  scales,  formed  by  overlapping  folds.  The  limbs 
are  stout ;  upon  the  anterior  feet  there  are  five,  upon  the 
posterior  four  claws.  On  the  under  surface  of  the  short 
tapering  tail  near  its  base  is  the  wide  opening  of  the  cloaca. 
The  ventral  plastron  consists  of  twelve  symmetrical  pieces, 
six  on  each  side,  Fig.  445.  The  first  and  last  pair  are  tri- 
angular, the  others  are  four-sided  ;  the  fourth  pair  is  the 

*This  description  has  been  prepared  and  the  illustrations  drawn  by 
Dr.  C.  S.  Minot. 


ANATOMY  OF  THE  TURTLE. 


507 


largest.  Underneath  the  epidermal  plates  are  nine  bony 
pieces.  The  dorsal  carapace  is  composed  of  thirty-eight 
plates,,  twenty-five  marginal,  of  which  the  most  anterior  lies 
in  the  middle  line  ;  there  are  five  median  plates  and  a  lateral 
row  of  four  plates  on  each  side. 

To  dissect  a  turtle,  saw  through  the  lateral  pieces  of  the 


Fig.  446.— Anatomy  of  the  Turtle,  Chrysemys  picta.— Drawn  by  C.  S.  Minot. 

shell  which  unite  the  plastron  and  carapace,  then  remove  the 
ventral  piece,  carefully  freeing  it  from  the  organs  beneath. 

Fig.  446  represents  a  female,  with  the  intestines  and  di- 
gestive glands  partially  freed  and  turned  aside,  while  the 
shoulder-blade,  oviduct,  and  ovary  of  the  left  side  and  the 


508  ZOOLOGY. 

right  lung  have  been  entirely  removed.  The  middle  line  of 
the  neck  is  occupied  by  the  trachea,  which  overlies  the  much 
wider  oesophagus,  which  again  rests  upon  two  very  large 
cylindrical  muscles,  the  powerful  retractors  of  the  head. 
The  muscles  (R)  extend  backwards  along  the  vertebral 
column,  behind  the  heart  and  through  the  abdomen.  The 
trachea  branches  just  in  front  of  the  heart,  to  send  a 
bronchus  to  each  lung.  The  left  bronchus  can  be  seen  in 
the  figure,  passing  between  the  pulmonary  artery  (p)  in 
front,  and  the  pulmonary  vein  behind  ;  the  three  tubes  run 
closely  parallel  forming  the  so-called  root  of  the  lung. 
Each  lung  (Lu)  is  a  large  elastic  sack  with  numerous  air- 
cells.  The  size  of  the  lung  depends  upon  its  degree  of  ex- 
pansion; when  entirely  collapsed  it  is  quite  small,  but  it  may 
easily  be  blown  up  through  the  trachea.  The  heart  (Hi)  is 
much  broader  than  in  the  frog  or  bird.  We  shall  recur  to 
its  structure  presently. 

Below  the  trachea  lies  the  much  larger  oesophagus,  a  cyl- 
indrical tube  with  muscular  walls.  The  oesophagus  termi- 
nates in  the  stomach  (S),  which,  together  with  the  remaining 
digestive  organs  and  the  spleen,  is  drawn  aside  in  the  figure. 
The  long  and  coiled  intestine  can  be  followed  to  the  point 
where  it  passes  under  the  oviducts  (ovd)  and  the  bladder 
(Bl]  to  terminate  in  the  cloaca,  the  external  opening  of 
which  is  represented  at  Cl.  The  main  mass  of  the  elongated, 
gray,  and  mottled  liver  lies  upon  the  intestine,  being  turned 
so  as  to  show  its  raphe  (m),  by  which  it  is  suspended  from  the 
peritonaeum,  the  portal  vein  (v),  and  the  retort-like  gall- 
bladder (G) ;  the  gall  duct  passes  through  the  body  of  the 
pancreas  (Pan),  an  elongated  whitish  mass  resting  upon  the 
first  coil  of  the  intestine,  the  so-called  duodenum.  Alongside 
the  pancreas  is  the  much  smaller  dark  oval  spleen  (Sp). 

The  specimen  figured  is  a  female  killed  during  the  period 
of  reproduction.  The  genital  organs  are  therefore  enor- 
mously developed.  The  long  and  prominent  oviducts  con- 
tained eggs  already  provided  with  a  shell.  The  right 
oviduct  is  seen  drawn  out  and  suspended  by  a  mesentery,  a 
thin  and  transparent  membrane  with  numerous  blood  ves- 
sels. The  lower  end  of  the  oviduct  is  seen  through  the 


ANATOMY  OF  THE  TURTLE. 


509 


mesentery,  and  contains  three  oval  eggs,  one  of  which  is 
lettered  Eg.  The  oviduct  can  be  followed  to  its  anterior 
end  which  is  much  pigmented  and  has  a  terminal  opening. 
The  cut-end  of  the  left  oviduct  (ovd)  shows  the  folds  of  the 
lining  mucous  membrane. 

The  ovary  (o)  is  likewise  suspended  by  a  thin  membrane, 
the  mesovarium,  and  is  equally  developed  on  both  sides  in  a 
complete  specimen.  It  is  easily  recognized  by  the  numerous 
bulging  yellow  spheres,  of  all  sizes,  which  are  the  egg-yolks 
in  various  stages  of  development. 

The  heart  of  the  turtle  (Fig.  447)  will  repay  careful  dis- 
section. A  small  round  body  lies  just  in  front  of  it ;  this  is 
usually  considered  the  equivalent  of  the  thyroid  gland, 
through  its  real  nature  is  still  un- 
certain. The  heart  itself  (Fig.  447) 
consists  of  two  auricles  and  one 
ventricle  (veri),  with  an  imper- 
fect internal  septum.  It  receives 
the  veins  upon  its  dorsal  surface, 
and  gives  off  the  arterial  trunks 
from  its  ventral  side.  The  two 
auricles  are  equal  in  size  ;  together 
they  a  little  more  than  equal  the 
ventricle.  The  arterial  vessels  arise 
together  a  little  to  the  right,  and 
are  most  conveniently  described  as 
three  in  number  :  1st.  The  right 
aorta  (R  Ad)  arising  on  the  left ; 
2d.  The  left  aorta  on  the  right  Fig. 

t  r     A   \        ,-,  .-I     •       the  heart  of  the  Turtle,  Chryse- 

(L  Ao)  ;     the    tWO    CrOSS    near   their     myspict,a.    Dissected  and  drawn 

origin  and  curve  upwards  and  back-    ] 

wards,  to  reunite  posteriorly  just  in  front  of  the  retractor 
muscles,  their  union  forming  the  single  median  descending 
aorta ;  3d.  The  pulmonary  aorta  (pa),  which  soon  divides 
into  a  branch  for  each  lung.  The  left  aorta  gives  off  a 
branch  (d)  which  persists  as  a  mere  cord,  the  remnant  of  the 
ductus  arteriosus,  which  originally  united  the  aorta  with  the 
pulmonary  artery.  The  right  aorta  gives  off  an  innominate 
branch,  that  soon  divides,  and  from  each  division  springs 


510  ZOOLOGY. 

the  carotis  (car),  and  subclavian  artery  of  the  same  side.  The 
veins  are  two  in  number,  as  they  enter  the  heart  :  1st.  The 
pulmonary  veins  (pv )  unite  to.  form  a  very  short  trunk 
emptying  into  the  left  auricle  ;  while  (2d)  the  two  venw 
caves  superiores  unite  with  the  cava  inferior  (V)  to  empty 
through  the  sinus  venosus  into  the  right  auricle. 

The  kidneys  lie  at  the  posterior  end  of  the  body  against 
the  vertebral  column.  In  the  figure  they  are  concealed  by 
the  bladder  and  oviducts.  (Minot.) 

There  are  about  forty  species  of  Chelonians  in  America 
north  of  Mexico.  The  lower  forms  of  turtles  are  the  marine 
species.  Such  is  the  great  sea-turtle  (Sphargis  coriacea 
Gray)  of  the  Atlantic  and  Mediterranean,  which  is  the 
largest  of  all  existing  turtles,  and  is  sometimes  eight  feet 
long,  weighing  from  eight  hundred  to  twelve  hundred  pounds. 
Next  to  this  species  is  the  loggerhead  turtle  (Thalassochelys 
caouana  Fitzinger),  which  is  sometimes  seen  asleep  in  mid- 
ocean.  Still  another  is  the  hawk-bill  or  tortoise-shell  turtle 
(Eretmochelys  imbricata  Fitz.),  the  plates  of  whose  shell  is 
an  article  of  commerce.  The  green-turtle  of  the  West 
Indies  weighs  from  two  hundred  to  three  hundred  pounds, 
and  is  used  for  making  delicious  soups  and  steaks  ;  being 
caught  at  night  when  laying  its  eggs  on  sandy  shores.  All 
the  foregoing  species  have  large,  flat,  broad  flippers  or  fin-like 
limbs,  while  in  the  pond  and  river  turtles  the  feet  are  webbed, 
and  the  toes  distinct.  A  very  ferocious  species  is  the  common 
soft-shelled  turtle  (Aspidonectes  spinifer  Lesueur),  whose 
shell  is  covered  with  a  thick  leathery  skin.  It  is  carnivorous, 
voracious,  living  in  shallow  muddy  water,  throwing  itself 
forward  upon  small  animals  forming  its  prey.  The  snap- 
ping-turtle  (Chelydra  serpentina  Schweigger)  sometimes 
becomes  five  feet  long  ;  its  ferocity  is  well  known  ;  the  flesh 
makes  an  excellent  soup. 

The  terrapins  belong  to  the  genus  Pseudemys  ;  the  pretty 
painted  turtle  (Chrysemys  picta  Agassiz)  is  common  in  the 
Eastern  States,  while  the  Nanemys  guttatus  (Agassiz),  or 
spotted  tortoise,  is  black,  spotted  with  orange.  In  the  land 
tortoises  the  feet  are  short  and  stumpy.  The  Testudo  Indica 
of  India  is  three  feet  in  length.  The  great  land  tortoises  of 


THE  ICHTHYOSAURS.  511 

the  Galapagos  Islands,  the  Mascarine  Islands  (Mauritius  and 
Rodriguez),  and  also  of  the  Aldabra  Islands,  lying  northwest 
of  Madagascar,  are  in  some  cases  colossal  in  size,  the  shells 
being  nearly  two  metres  (six  feet)  in  length.  The  fierce  Mas- 
carine species  were  contemporaries  of  the  dodo  and  solitaire, 
and  are  now  extinct.  The  bones  of  extinct  similar  species 
have  been  found  in  Malta  and  in  one  of  the  West  Indian 
islands.  The  land  tortoises  are  long-lived  and  often  reach  a 
great  age.  Certain  tortoises  of  the  Tertiary  Period,  as  the 
Colossoclielys  of  the  Himalayas  had  a  shell  twelve  feet  long 
and  six  feet  high.  The  turtles  extend  back  in  geological 
time  to  the  Jurassic,  a  species  of  Compsemys  being  char- 
acteristic of  the  Upper  Jurassic  beds  of  the  Rocky  Moun- 
tains. (Marsh.) 

The  eggs  of  turtles,  as  those  of  birds,  are  of  large  size  ; 
they  are  buried  in  June  in  the  sand  and  left  to  be  hatched 
by  the  warmth  of  the  sun.  It  is  probable  that  turtles  do  not 
lay  eggs  until  eleven  to  thirteen  years  of  age.  The  develop- 
ment of  turtles  is  much  as  in  the  chick.  By  the  time  the 
heart  becomes  three -chambered,  the  vertebrae  develop  as  far 
as  the  root  of  the  tail,  and  the  eyes  are  completely  enclosed 
in  their  orbits.  The  shield  begins  to'develop  as  lateral  folds 
along  the  sides  of  the  body,  the  narrow  ribs  extending  to  the 
edge  of  the  shield.  In  the  lower  forms  of  turtles  (the 
Clielonioidce),  the  paddle-like  feet  are  formed  by  the  bones  of 
the  toe  becoming  very  long,  while  the  web  is  hardened  by 
the  development  of  densely  packed  scales,  so  that  the  foot  is 
nearly  as  rigid  as  the  blade  of  an  oar. 

Orders.  Rhynclioceplialia. — The  only  living  representa- 
tive of  this  order  is  the  Splienodon  or  Hatteria  of  New  Zea- 
land ;  a  lizard-like  form  of  simpler  structure,  however,  than 
the  lizards  in  general.  This  rare  creature  somewhat  re- 
sembles an  iguana  in  appearance,  having  a  dorsal  row  of 

>ines.  It  is  nearly  a  metre  (32  inches)  in  length.  In  this 
jroup  the  vertebrae  are  biconcave  ;  the  quadrate  bone  is  im- 

lovable,  and  there  are  other  important  characters  based  on 
a  study  of  the  living  and  fossil  forms,  the  latter  represented 
by  the  Triassic  Rhyncliosaurus  and  Hyperodapedon. 

Order  G.   Iclithyopteryyia. — This  order  is  entirely  extinct. 


512 


ZOOLOGY. 


The  Ichthyosaurs  were  colossal  reptiles  from  two  to  thirteen 
metres  (six  to  forty  feet)  in  length,  swimming  in  the  ocean  by 
four  paddle-like  limbs  consisting  of  six  rows  of  digital  bones  ; 


I 


Fob 


Fig.  448.— Skull  of  Ichthyosaurus  ;  lateral  view.  Pmx,  premaxillary  bone  ;  MX, 
maxillary  ;  N,  nasal ;  Fr,  frontal ;  Prf,  prefrontal ;  Pof,  postfrontal ;  Pa,  parietal ; 
L,  lachrymal;  M,  malar;  Qj,  quadrat  oj  ugal  ;  Q,  quadrate;  Pob,  postorbital  ;  Sq, 
squamosal ;  D,  dentary ;  Ang,  angular  ;  Art,  articular  ;  S.  Ar,  subarticular  ;  Pter, 
pterygoid.— After  Cope. 

the  head  was  very  large,  the  neck  very  short,  and  the  orbits 
were  enormous  ;  the  vertebras  were  remarkably  short  and  bi- 
concave. They  were  carniv- 
orous, and  powerful  swim- 
mers, and  common  in  the  Ju- 
rassic seas  of  Europe ;  one 
form  existed  in  the  Jurassic 
times  in  Wyoming. 

Order  7.  Theromorplia. — 
This  order  is  divided  into  the 
Pelycosauria  and  Anomo- 
dontia.  The  beaked  Saurians 
were  somewhat  lizard-like,  but 
Fig.  449.-post"rior  view  of  the  skuii  of  were  synthetic  types,  combin- 

Ichthyo*aurus ;   lettering  as  in  Fig.  443,     .         .,         ,  L  £    >i       T   i 

with  following  additions  ;  Bo,  basiocci-  mg  the  characters  of  the  Icll- 
pital ;  JSjio,  Exoccipital  ;  Sup.  0.  supra-  . -,  , ••  ,  ,-1  / -\ 

occipital ;  Opo,  opistiiotic ;  stap,  supra-  thyosaurs,    the    turtles,    tne 

stapedialorhyornandibular.-AfterCope.     ^^^   with  those  of   liz- 

ards,  Dinosaurians,  and  crocodiles.  The  skull  was  short, 
and  in  Dicynodon  the  jaws  in  front  had  the  nipping,  horny 
beak  of  a  turtle,  while  from  behind  in  the  upper  jaw  pro- 
truded two  long,  curved,  canine  teeth.  Dicynodon  figriceps 
Owen,  had  a  skull  about  half  a  metre  (20  inches)  long. 


THE  PLESIOSAUR8. 


513 


Another  form  was  still  more  like  the  turtles,  the  jaws  being 
toothless  and  enclosed  in  a  nipping,  horny  beak.  In  Lys- 
trosaurus  (Fig.  450)  the  head  was  blunt,  the  jaws  armed  in 
front  with  stout  teeth,  and  behind  with  canine  teeth ;  and 
these  animals,  anticipating  in  their  dentition  the  lions  arid 
tigers,  were  called  by  Owen  Theriodonts  (beast-toothed). 
These  forms  lived  during  the  Permian  and  Triassic  times. 
Order  8.  Sauropterygia. — The  Plesiosaurus  is  the  type 


—  Ptf 


Ftg.  450. — Skull  of  Lystrosaurns  frontosus  from  Cape  Colony.  Profile.  Lettering 
as  in  Fig.  443  and  444,  with  the  following  additions  :  Etvom,  ethmovomerinc  ;  Sph, 
sphenoid;  pro,  ProotSc;  Pter,  Pterygoid  ;  Col,  Columella  ;  Ectp,  Ectopterygoid  ; 
Subart,  subarticular  bone.— From  Cope. 

of  this  extinct  order.  The  Plesiosaurs  were  somewhat  like 
the  Ichthyosaurs,  swimming  by  paddle-like  feet,  but  the  neck 
was  very  long,  and  the  head  rather  small.  The  largest  true 
Plesiosaur  was  about  nine  metres  in  length.  They  abounded 
during  the  Jurassic  and  Cretaceous  period.  During  the  lat- 
ter period  off  the  coast  of  New  Jersey  and  in  the  seas  of 
Kansas  nourished  huge  Plesiosaurian  reptiles,  such  as  Elas- 
mosaurus,  which  had  an  enormous  compressed  tail.  The 


514  ZOOLOGY. 

vertebrae  of  E.  platyurus  Cope,  of  the  New  Jersey  marl- 
beds,  had  vertebrae  nearly  as  large  as  those  of  an  elephant, 
while  the  creature  was  whale-like  in  bulk,  the  neck  long  and 
flexible,  the  paddles  short.  The  skull  was  light,  with  a 
long,  narrow,  very  flat  muzzle,  It  must  have  been  the  ter- 
ror of  those  times  ;  it  was  about  fifteen  metres  (45  feet) 
in  length.  (Cope.) 

Order  9.  Crocodilia. — The  crocodile,  caiman,  gavial,  and 
alligator  are  the  types  of  this  well-known  group.  They  pre- 
sent a  decided  step  in  advance  of  other  reptiles,  the  heart 
approaching  that  of  birds,  in  having  the  ventricle  completely 
divided  by  a  septum  into  two  chambers  ;  the  venous  and  arte- 
rial blood  mingle  outside  of  the  heart,  not  in  it,  as  in  the 
foregoing  living  orders.  The  brain  is  also  more  like  that  of 
birds,  the  cerebellum  being  broader  than  in  the  other  rep- 
tiles. The  nostrils  are 
capable  of  closing,  so 
that  crocodiles  and 
alligators  draw  their 
prey  under  the  water 
and  hold  them  there 
until  they  are  drown- 
ed ;  but  they  are 

Fig.  451.-Head  of  the  Florida  Crocodile.-After    obliged   to   drag   them 

Hornaday.  ashore  in  order  to  eat 

them.  The  skin  is  covered  with  bony,  epidermal  scales.  The 
conical  teeth  are  lodged  in  sockets  in  the  jaws.  The  vertebrae 
are  concave  in  front  and  convex  behind,  or  the  reverse  ;  the 
quadrate  bone  is  immovable.  The  feet  are  partly  webbed. 
The  crocodiles  and  gavials  appeared  during  the  Jurassic  pe- 
riod, but  the  early  forms  were  marine  and  like  gavials,  the 
head  being  long  and  narrow  in  front,  with  biconcave  verte- 
brae. They  lay  from  twenty  to  thirty  cylindrical  eggs  in  the 
sand  on  river  banks.  The  crocodiles  are  distributed  through- 
out the  tropics,  even  Australia ;  the  gavials  are  mostly  con- 
fined to  India  and  Malaysia,  and  also  Australia.  The  group 
is  represented  in  the  Southern  States  by  the  alligator  (A. 
Mississippiensis  Daudin).  It  is  nearly  four  metres  (10-12 
feet)  long;  while  the  Florida  crocodile  (0.  acutus  Cuvier, 


DINOSAURIAN  REPTILES.  515 

Fig.  451)  in  which  the  jaws  are  much  narrower,  is  over  four 
and  a  half  metres  (14  feet)  long.  It  inhabits  the  rivers  of 
Florida  where  it  is  very  rare,  and  also  the  West  Indies  and 
South  America.  The  cayman  of  Guiana  belongs  to  a  dis- 
tinct genus,  Caiman,  and  is  characteristic  of  the  rivers  of 
tropical  South  America. 

Order  10.  Dinosauria. — We  now  come  to  reptiles  which 
have  more  decided  affinities  as  regards  their  skeleton  (the 
only  parts  preserved  to  us)  to  the  birds,  especially  the  os- 
triches, than  any  reptiles  yet  mentioned  ;  while  the  Dino- 
saurs were  genuine  reptiles,  in  the  pelvis  and  hind  limbs, 
including  the  feet,  they  approached  the  birds.  This  is  seen 
especially  in  the  ischium,  which  is  long,  slender,  and  inclined 
backwards  as  in  birds.  In  the  hind  limbs  the  resemblance 
to  birds  is  seen  ;  among  other  points,  in  the  ascending  pro- 
cess of  the  astragalus,  in  the  position  of  the  farther  (distal) 
end  of  the  fibula,  and  in  their  having  only  three  functional 
toes.  The  fore  limbs  were  shorter  and  smaller  than  the 
hind  extremities,  sometimes  remarkably  so.  Moreover,  the 
limb-bones,  vertebrae,  and  their  processes  were  sometimes 
hollow  ;  the  sacrum  consisted  of  four  or  five  consolidated 
vertebrae,  in  this  respect  anticipating  the  birds  and  mam- 
mals. They  walked  with  a  free  step,  like  quadrupeds, 
instead  of  crawling  like  reptiles  ;  some  walked  on  the  hind 
legs  alone,  making  a  three-toed  footprint,  occasionally 
putting  down  the  forefoot,  like  the  kangaroo.  The  lar- 
gest Dinosaurs  were  the  Iguanodon,  which  was  from  ten 
to  sixteen  metres  (30-50  feet)  in  length,  and  the  Cama- 
rasaurus  (Atlantosaurus)  which  was  about  twenty-seven 
metres  (80  feet)  in  length.  The  Cetiosaurus  had  a  length  of 
from  twenty  to  twenty-three  metres  (60-70  feet).  The  Ha- 
drosaurus  stood  on  its  ponderous  hind  legs,  with  a  stature  of 
over  eight  metres  (25  feet).  These  were  bulky,  inoffensive, 
herbivorous  monsters,  able  to  rise  up  on  their  hind  feet  and 
browse  on  the  tops  of  trees ;  their  undue  increase  was 
prevented  by  carnivorous  forms  like  Lcelaps,  which  was  an 
active,  possibly  warm-blooded  Dinosaur,  with  light,  hollow 
bones,  large  claws,  and  serrate,  conical  teeth.  It  stood  six 
metres  (18  feet)  high,  and  could  leap  a  distance  of  ten 
metres  through  the  air.  (Cope.) 


516  ZOOLOGY. 

Still  nearer  the  birds  was  the  Compsognatlms ;  it  was 
only  two  thirds  of  a  meter  (2  feet)  long,  with  a  light  head, 
toothed  jaws,  and  a  very  long,  slender  neck  ;  the  hind  limbs 
were  very  large  and  disposed  as  in  birds,  the  femur  being 
shorter  than  the  tibia ;  moreover,  the  fore  legs  were  very 
small.  "It  is  impossible,"  says  Huxley,  "to  look  at  the 
conformation  of  this  strange  reptile  and  to  doubt  that  it 
hopped  or  walked,  in  an  erect  or  semi-erect  position,  after 
the  manner  of  a  bird,  to  which  its  long  neck,  slight  head, 
and  small  anterior  limbs  must  have  given  it  an  extraordi- 
nary resemblance."  The  so-called  bird  tracks  of  the  Triassic 
rocks  of  the  valley  of  the  Connecticut  were  all  reptilian 
footprints,  and  without  doubt  made  by  Dinosaurs  with  the 
above-mentioned  affinities  to  the  birds.  These  bird-like, 
colossal  lizards  appeared  in  the  Jura-Trias  Period,  and  be- 
came extinct  in  late  Cretaceous  times. 

Order  11.  Pterosauria. — The  forms  of  this  order,  rep- 
resented by  the  Pterodactyles,  would  lead  one  to  infer  that  the 
group  was  still  more  bird-like  than  the  Dinosaurs,  and  See- 
ley  has  shown  that  they  have  as  many  and  important  points 
of  similarity  to  that  class  as  the  preceding  group.  They  are 
a  sort  of  reptilian  bats,  forming  links  between  reptiles  and 
flying  birds,  as  the  Dinosaurs  connect  with  the  ostriches, 
and  it  is  in  the  hand  and  foot,  which  in  birds  are  the  most 
characteristically  ornithic,  that  they  resemble  the  ornithic 
type.  They  also  approach  birds  in  their  long  heads  and 
necks,  the  jaws  with  or  without  teeth,  the  short  tail,  in  the 
skull  which  is  more  rounded  and  bird-like  than  in  other 
reptiles,  with  large  orbits,  as  also  in  the  form  of  the  brain  ; 
while  the  jaws  were  probably,  in  part  at  least,  encased  in 
horny  beaks.  The  shoulder  girdle  was  bird-like,  and  the 
sternum  was  keeled,  but  the  pelvis  and  limbs  were  like 
those  of  lizards,  while  the  fore-feet  were  much  larger  than 
the  hinder  ones,  and  the  ulnar  finger  was  enormously 
long  and  probably  supported  a  broad  membrane,  connecting 
the  fore  and  hind  limbs,  as  in  bats;  moreover,  the  limb 
bones  were  hollow,  and  air-cells  were  present,  so  that 
these  winged  lizards  could  fly  like  birds  or  bats.  The  jaws 
of  the  Pterosaurs  were  completely  toothed ;  those  of  the 


CLASSIFICATION  OF  REPTILES.  517 

Rhampliorhynclius  had  teeth  in  the  back  of  the  jaw,  the 
ends  of  the  jaws  being  toothless  and  probably  encased  in 
horny  beaks,  while  in  Pteranodon  the  jaws  were  toothless. 
They  were  of  different  size,  some  expanding  only  as  much 
as  a  sparrow,  others  with  a  spread  of  about  nine  metres  (27 
feet).  They  were  contemporaries  of  the  Dinosaurs,  several 
forms,  discovered  by  Marsh,  occurring  in  the  Cretaceous 
beds  of  Kansas. 


CLASS  V.   REPTILIA. 

Air-breathing  Vertebrates,  with  limbs  usually  ending  in  claws;  limbs 
sometimes  absent,  rarely  paddle-shaped  ;  body  scaled  ;  ribs  well  developed  ; 
heart  in  the  highest  forms  four-chambered;  'cold  blooded;  an  incomplete 
double  circulation ;  oviparous;  eggs  large;  embry )  iDith  an  amnion  and 
allantois  ;  no  metamorphosis. 

Order  1.  Ophidia. — Body  long,  cylindrical,  visually  limbless  ;  no  shoul- 
der  girdle.  (Eutsenia.) 

Order  2.  Fythonomorpha. — Extinct,  snake-like,  limbs  paddle-shaped. 
(Mosasaurus.) 

Order  3.  Lacertilia. — Body  with  a  long  tail;  usually  four  limbs;  mouth 
not  dilatable,  the  bones  of  the  jaw  being  firm.  (Sceleporus.) 

Order  4.  Chelonia. — Body  enclosed  in  a  thick  shell,  within  which  the 
head  and  limbs  can  be  withdrawn.  (Testudo.) 

Order  5.  RhynchocepJialia. — Lizard-like  ;  vertebrae  bi-concave,  species 
mostly  extinct.  (Sphenodon.) 

Order  6.  Ichthyopterygia. — Head  large,  orbits  large;  limbs  paddle- 
shaped;  extinct  forms.  (Ichthyosaurus.) 

Order  7.  Theromorpha. — Mammal-like  saurians  with  solid  pelvis  and 
shoulder-girdle,  and  with  canines,  or  toothless  and  beaked. 
(Dicynodon.) 

Order  8.  Sauropterygia. — Extinct  colossal  saurians,  with  long  necks, 
head  of  moderate  size.  (Elasmosaurus.) 

Order  9.  Crocodilia. — Thick  -  scaled  ;  heart  four-chambered.  (Croco- 
dilus.) 

Order  10.  Dinosauria. — Colossal  extinct  saurians,  capable  of  rising 
and  resting  on  the  hind  legs,  and  making  three-toed  tracks. 
(Hadrosaurus.) 

Order  11.  Pterosauria. — Extinct  flying  saurians,  with  the  fore  limbs 
large  and  a  very  long  ulnar  finger;  toothed  or  toothless. 
(Pterodactyl  us.) 


518  ZOOLOGY. 


CLASS  VI.  AVES  (Birds), 

General  Characters  of  Birds. — We  have  met  in  the  rep- 
tiles, especially  in  the  fossil  forms,  many  characters  indicat- 
ing that  birds  are  by  no  means  so  specialized  or  so  well 
circumscribed  a  group  as  was  formerly  supposed.  Such  a 
relationship  between  the  two  classes  has  recently  been  still 
further  exhibited  by  Meyer's  discovery  of  Archmopteryx  litho- 
graphica  of  the  Solenhofen  slates  of  the  Jurassic  beds  of 
Germany,  and  by  Marsh's  discovery  of  birds  with  teeth  and 
biconcave  vertebrae  in  the  Cretaceous  rocks  of  JSForth  Ameri- 
ca. On  account,  therefore,  of  the  close  relations  between 
birds  and  reptiles,  Huxley  has  placed  these  two  classes  in  a 
series  called  Sauropsida,  which  may  be  opposed  to  the  Icli- 
thyopsida  (Fishes  and  Batrachians)  on  the  one  hand,  and 
the  Mammalia  on  the  other,  by  the  following  characters  : — 

Sauropsida. — There  are  no  mammary  glands.  There  is 
an  amnion  and  an  allantois  ;  the  species  are  oviparous  or 
ovoviviparous,  with  reproductive  organs  and  digestive  caual 
opening  into  a  common  cloaca,  and  "Wolffian  bodies  replaced 
functionally  by  permanent  kidneys.  There  is  no  corpus 
callosum,  nor  complete  diaphragm.  Respiration  is  effected 
by  lungs,  never  by  gills.  The  heart  is  two  or  three  cham- 
bered, and  there  are  usually  two  or  three  aortic  arches ;  in 
birds  but  one  ;  there  are  red  oval  nucleated  blood  corpuscles. 
The  bodies  of  the  vertebras  are  ossified,  but  without  terminal 
epiphyses.  There  is  a  single  convex,  occipital  condyle,  in 
connection  with  an  ossified  basi-occipital.  The  ramus  of 
the  mandible  consists  of  several  pieces,  the  articular  one  of 
which  is  connected  with  the  skull  by  a  quadrate  bone.  The 
ankle-joint  is  between  the  proximal  and  distal  divisions  of 
the  tarsus.  The  skin  usually  developes  scales  or  feathers. 

These  important  characters,  derived  from  Huxley  (as  are 
many  of  those  given  beyond  for  the  class  Aves),  may  remind 
the  student  of  the  actual  affinities  between  birds  and  rep- 
tiles. The  former  are  distinguished  from  other  Sauropsida 
by  the  following  peculiarities  : — 

Aves. — The  body  is  covered  with  feathers,  a  kind  of  der- 
mal outgrowth  found  in  no  other  animals.  The  fore  limbs 


STRUCTURE  OF  BIRDS.  519 

form  wings,  serviceable  in  nearly  all  cases  for  flight.  There 
are  never  more  than  three  digits  in  the  hand,  two  of  them 
usually  much  reduced,  and  none  of  them  bearing  claws 
(with  rare  exceptions);  nor  more  than  two  separate  carpal 
bones  in  adult  recent  birds  ;  nor  any  separate  interclavicle  ; 
the  clavicles  are  normally  complete,  and  coalesce  to  form  a 
"merry  -  thought."  The  sternum  is  large,  and  usually 
keeled  (the  only  exception  among  recent  forms  being  the 
struthious  birds);  it  ossifies  from  two  to  five  or  more  centres, 
and  the  ribs  are  attached  to  its  sides.  The  skull  articulates 
with  the  spinal  column  by  a  single  median  convex  condyle, 
developed  in  connection  with  a  large  ossified  basi-occipital. 
The  lower  jaw  consists  of  several  pieces,  articulated  by  a 
quadrate  bone  to  the  skull,  and  in  all  recent  birds  both  jaws 
are  toothless  and  encased  in  a  horny  beak.  The  bodies  of 
at  least  some  of  the  vertebrae  of  recent  birds  have  sub-cyclin- 
drical,  articular  faces  ;  when  these  faces  are  spheroidal,  they 
are  opisthocoelian,  but  some  fossil  forms  are  amphicoelian. 
The  proper  sacral  vertebrae  have  no  expanded  ribs  abutting 
against  the  ilia.  The  ilia  are  greatly  prolonged  forwards ; 
the  acetabulum  is  a  ring,  not  a  cup  ;  the  ischia  and  pubes 
are  prolonged  backwards  ;  there  is  no  ischial  symphysis  ; 
there  may  be  a  prepubis ;  a  process  of  the  astragalus  early 
anchyloses  with  the  tibia.  The  incomplete  fibula  does  not 
reach  the  ankle-joint;  there  are  not  more  than  four  digits, 
the  normal  numbers  of  phalanges  of  which  are  2,  3,  4,  5. 
The  1st  metatarsal  is  incomplete  above  ;  the  3d,  3d  and  4th 
anchylose  together,  and  with  the  distal  tarsal  bone  unite  to 
form  a  tarso-metatarsus.  The  heart  is  completely  four-cham- 
bered ;  there  is  but  one  aortic  arch  (the  right),  and  but  one 
pulmonic  -t*unk  from  the  right  ventricle  ;  the  blood  is  red 
and  hot.  The  large  lungs  are  not  free  in  the  cavity  of  the 
thorax,  but  fixed  and  moulded  to  the  walls  of  that  cavity ; 
and  in  all  recent  birds  the  larger  air-passages  of  the  lungs 
terminate  in  air-sacs.  More  or  fewer  of  the  bones  are 
usually  hollow,  and  permeable  to  air  from  the  lungs.  There 
is  at  most  a  rudimentary  diaphragm.  The  eggs  are  very  large, 
in  consequence  of  a  copious  supply  of  albuminous  substance, 
in  the  form  of  yolk  and  white,  and  are  enclosed  in  a  hard 


520 


ZOOLOGY. 


12  13 

/\      / 


14 


15 


IV  II 

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A 


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II  \  ¥ 


4544434241403938  37  36    35    34    .33    3231302928    27    26     25     24 


Fig.  452.— Topography  of  a  bird.  1,  forehead  (front) ;  2,  lore  ;  3,  circumorular 
region  ;  4,  crown  (vertex) ;  5,  eye ;  fi,  hind  head  (occiput)  ;  7,  nape  (nucha) ;  8,  hind 
neck  (cervix) ;  9,  side  of  neck  ;  10,  interscapular  region  ;  11,  dorsum  or  back  proper, 
including  10;  12,  notceum,  or  upper  part  of  body  proper,  including  10.  11  and  13; 
13,  rump  (uropygium);  14,  upper  tail  coverts;  15,  tail  ;  16,  under  tail  coverts  ;  17, 
tarsus ;  18,  abdomen  ;  19,  hind  toe  (hallux)  ;  20,  qastrwum,  including  18  and  24  ;  21, 
outer  or  fourth  toe  ;  22,  middle  or  third  toe  ;  23,  side  of  the  body  ;  24,  breast  (pectus); 
25.  primaries;  26,  secondaries  ;  27,  tertiaries,  Nos.  25,  26,  27  are  all  remiges;  28, 
primary  coverts  ;  29,  alula,  or  bastard  wing  ;  30.  greater  coverts  ;  31,  median  coverts  ; 
32,  lesser  coverts :  .33,  the  "throat,"  including  34,  37  and  38;  34,  jugulum,  or  lower 
throat :  35,  auriculars ;  36,  malar  region ;  37,  gula  or  middle  throat ;  38,  mentum  or 
chin  ;  39,  angle  of  commissure,  or  corner  of  mouth  ;  40,  ramus  of  under  man- 
dible ;  41,  side  of  under  mandible  ;  42,  gonys ;  43,  apex,  or  tip  of  bill  ;  44,  tomia.  or 
cutting  edges  of  the  bill ;  45,  oilmen,  or  ridge  of  upper  mandible,  corresponding  to 
gonys  ;  46,  side  of  upper  mandible  ;  47,  nostril ;  48,  passes  across  the  bill  a  little  in 
front  of  its  face.— Prom  Coues's  Key. 


STRUCTURE  OF  BIRDS.  521 

calcareous  shell  ;  there  is  an  amnion  and  allantois,  and  no 
metamorphosis  after  hatching. 

The  external  form  of  birds  is  very  persistent  ;  the  different 
parts  of  the  body  have  been  named  in  terms  of  continual  use 
in  descriptive  ornithology.  Hence,  without  entering  into 
details,  we  reproduce  from  Coues's  "Key"  his  figure  of  the 
topography  of  a  bird. 

The  student,  after  a  careful  study  of  the  external  form, 
should  prepare  a  skeleton  of  the  common  fowl,  or  examine  one 
already  at  hand,  and  observe  those  characters  peculiar  to  birds. 
The  skull  is  formed  of  bones  consolidated  into  a  more  roomy 
brain-box  than  in  any  reptiles,  unless  it  be  the  Pterosaurians. 
In  the  parrots  the  beak  of  the  upper  jaw  is  articulated  (Fig. 
453,  n)  to  the  skull,  so  that  the  movement  of  the  beak  on  the 
skull  is  unusually  free.  The 
quadrate  bone  (Fig.  453,  e)  is 
usually  movable  on  the  skull  ; 
and  in  the  parrots  when  the 
mouth  opens  the  upper  jaw  rises, 
since  when  the  mandible  is  low- 
ered, the  maxillo  -  iugal  rod 

/T^-         ^ro      7\             i  FiS-  458-—  Skull  of  Parrot:  22,  pre- 

Ol*    bar    (X  lg.    45o,    /)    pushes  the  maxillary  bone  ensheathed  in  horn  ; 

/n^\                      i  -i  15'  nasal  bones  ;    v,  mandible,  the 

(22)      Upwards  and  end  sheathed  with  horn-    /,  malo- 


forwards.  This  is  a  constant  fea- 
ture  in  recent  birds,  the  degree 
of  motion  which  this  peculiar 
mechanism  allows  being  variable.  Owen- 

The  form  of  a  bird's  vertebrae  is  peculiar  to  the  class  ;  the 
articulation  of  the  body  (centrum)  in  all  the  vertebrae  in 
front  of  the  sacrum  being  saddle-shaped.  "In  Strigops 
and  a  few  other  land  birds  ;  in  the  penguins,  the  terns,  and 
some  other  aquatic  birds,  one  or  more  vertebrae  in  the  dor- 
sal region  are  without  the  saddle-shaped  articulation,  and 
are  either  opisthocoelian,  or  imperfectly  biconcave."  (Marsh.) 
In  the  fossil  Ichthyornis,  which  had  a  powerful  flight,  the 
vertebrae  are  bi-concave,  as  in  fishes,  and  Amphibians,  and 
a  few  reptiles  ;  but  the  third  cervical  shows  an  approach  to 
the  saddle  -  vertebrae  of  all  other  birds.  The  saddle  form 
renders  the  articulation  strong  and  free,  and  especially 
adapted  to  motion  in  a  vertical  plane.  (Marsh.) 


ZOOLOGY. 


While  the  sternum  of  the  cassowaries  and  other  struthious 
birds  (Ratitce)  is  smooth,  approaching  that  of  reptiles,  that 
of  the  higher  living  birds  is  keeled  or  carinate  (Fig.  454, 
crs) ;  hence  these  birds  are  called  Cari- 
natce ;  to  this  keel  and  neighboring  parts 
the  muscles  which  raise  and  lower  the  wings 
are  attached. 

The  fore  limbs  of  birds  (Fig.  455)  are 
greatly  modified  to  form  the  framework  of 
the  wings.  In  spreading  and  closing  the 
wings,  the  bones  of  the  forearm  slide  along 
each  other  in  a  peculiar  manner.  (Cones.) 
The  ulna  is  usually  thicker  and  longer  than 
the  radius,  and  there  are  only  two  carpal 
bones,  one  radial,  the  other  ulnar,  in  adult 
recent  birds.  The  hand  in  the  Apteryx  and 
Fig.  454.— sternum  cassowaries  has  but  one  complete  digit, 

of  the  Guinea    Hen,  .  .  «     ' 

eeen  from  in  front;  while  in  other  DUOS  there  are  three  digits, 

crs,  crest ;  c,  coracoid        -i  •   i  111  TI/IO 

bone.— After  Gegen-  which  probably  correspond  to  the  first, 
second,  and  third  fingers  of  the  human 
hand.  The  wings  are  attached  to  a  strong  shoulder-girdle, 
which  consists  of  the  two  collar  bones,  uniting  to  form  the 
wish-bone,  and  of  a  coracoid  bone  and  scapula. 


Fig.  455.-  -Right  wing  hones  of  a  young  Chicken.  A,  shoulder  ;  B,  elbow ;  C,  wrist 
or  carpus ;  Z>,  tip  of  third  finger  ;  a,  humerus  ;  &,  ulna  ;  c,  radius ;  d,  scapholunar 
bone  ;  «?,  cuneiform  bone ;  /,  </,  epiphysea  of  metacarpal  bones  I.  k,  respectively  ;  h, 
metacarpal  and  its  digit  i.— From  Coues'sKey. 

The  pelvis  of  birds  is  remarkable  for  the  long  slender  back- 
wardly  projecting  ischium  and  pubic  bones;  there  is  generally 


STRUCTURE  OF  BIRDS. 


523 


no  bony  union  of  the  two  pubic  bones,  nor  do  the  ischia 

unite  with  the  sacrum  or  each  other,  except  in  Rhea.     In  the 

ostrich,  the  pubic  bones  are  solidly  united.     The  hind  limbs 

(Fig.  456)  are  two,  three,  or  four  toed,  the  ostrich  having 

but  two  digits  ;  in  most  four-toed  birds,  one  toe  (the  hallux) 

is  directed  backwards,  while  in  the  parrots  and  trogons, 

etc.,  there  are  two  toes  in  front  and  two  toes  -behind,  and 

in   the   swifts   and  certain   other  forms   all 

four  toes  are  turned  forwards.     The  bones  of 

the  skeleton  are  dense  and  hard  ;  both  the 

long  bones  and  the  bones  of  the  skull  are 

commonly  hollow,  containing  air;  the  air-sacs, 

in  connection  with  the  lungs,  communicating 

with  the  hollows  of  the  bone.     In  some  birds 

which  fly  well,  only  the  skull-bones  have  air- 

cells,  while  in  the  ostrich  which  is  unable  to 

fly,  the  bones  have  even  a  greater  number  of 

cavities   than   the   gull.     The   body   during 

flight  is  thus  greatly  lightened,  and  the  bird 

can  sustain  itself  in  the  air  for  many  hours  in 

succession. 

With  all  these  characters,  the  most  re- 
markable and  diagnostic  external  feature  is 
the  presence  of  feathers;  no  reptile  on  the 
one  hand,  or  mammal  on  the  other,  is  clothed 
with  feathers,  though  the  scales  on  the  legs 
and  feet  of  birds  are  like  those  of  reptiles, 
and  it  should  be  borne  in  mind  that  feathers 
are  fundamentally  modified  scales  or  hairs. 
The  ordinary  feathers  are  called  pennae  or 

_•*  •*•  , 

contour  feathers  ;  as  they  determine  by  their  seen  from  in  front; 

,    ,!  ,-,.  „    ,  r™  <ld',  d"d"',  the  four 

arrangement  the  outline  ot  the  body.  They  toes.—  After  oegen- 
are,  like  hairs,  developed  in  sacs  in  the  skin  ;  l 
the  quill  is  hollow,  partly  imbedded  in  the  derm  ;  this  merges 
into  the  shaft,  leaving  the  outgrowths  on  each  side  called  barbs, 
which  send  off  secondary  processes  called  barbules.  These 
tertiary  processes  (called  barbules  and  hooklets)  are  com- 
monly serrated,  and  end  in  little  hooks  by  which  the  bar- 
bules interlock.  Down  is  formed  of  feathers  with  soft, 


Fig  456  __  Hind 


theaame 

piece  isolated,  and 


524 


ZOOLOGY. 


free  barbs,  called  plumules.     Over  the  tail-bone  (coccytf  are 
usually  sebaceous  glands,  which  secrete  an  oil,  used  by  the 

bird  in  oiling  and  dress- 
ing or  "preening"  its 
feathers.  In  some  birds, 
especially  in  the  males  of 
the  gallinaceous  fowls,  as 
the  cock  and  turkey,  the 
head  and  neck  are  orna- 
mented with  naked  folds 
of  the  skin  called  "  combs" 

Fig.  457.— Brain  of  the  Hen.  A ,  from  above,  ,, 

B,  from  below  ;   a,  olfactory  bulbs  ;   b,  cere-  and       wattles, 
bral  hemispheres ;  c,  optic  lobes ;  d,  cerebel-         mi      .... 
lum  ;   d',  its  lateral  parts  ;  e,  medulla.— After          lllC  braill  IS  mucll  larger 

Cams,  from  Gegenbaur.  ,-,  xl  ,.-,  ,-. 

than  in  the   reptiles,   the 

cerebral  hemispheres  being  greatly  increased  in  size,  while 
the  cerebellum  is  transversely  furrowed,  and  is  so  large  as  to 
cover  the  whole  of  the  me- 
dulla. The  alimentary  tract 
consists  of  an  O3sophagus  as 
long  as  the  neck ;  it  dilates 
in  the  domestic  fowl  and  other 
seed-eating  birds,  as  well  as 
in  the  raptorial  birds,  into  a 
lateral  sac  called  the  crop  (in- 
gluvies).  The  stomach  is  di- 
vided into  two  parts,  the  first, 
the  proventricultte,  which  is 
glandular,  secreting  a  digest- 
ive fluid  ;  and  the  second, 
which  corresponds  to  the  pylo- 
ri c  end  of  the  stomach  in  the 
mammals,  is  round,  with  mus- 
cular walls,  especially  develop- 
ed in  seed-eating  birds,  and 
called  the  "gizzard."  In  the 

•      i  .-,         .  -,    .     -..       j       .,-•      glands  of  a  young  hawk,  Buteo  milgaris 

fowl  the  gizzard  IS  lined  With    of  Europe  ;    tr,  trachea.-After  Gegen- 

a  firm  horny  layer,  by  which  * 

the  food  is  crushed  and  comminuted,  thus  taking  the  place 

of  teeth.    The  intestine  (including  the  large  and  small  intes- 


Fig.  458.— Thymus  (th)  and  thyroid  (f) 


ANATOMY  OF  THE  PIGEON.  525 

tine)  is  long  and  ends  in  a  cloaca,  which  receives  the  ends 
of  the  urinary  canals  and  oviducts.  Attention  should  be 
given  to  the  trachea  ;  its  bronchial  branches,  the  larynx  and 
the  syrinx  or  lower  larynx,  which  may  be  developed  either 
at  the  end  of  the  trachea,  or  at  the  junction  of  the  trachea 
and  bronchi,  or  in  the  bronchi  alone.  The  thymus  gland 
(Fig.  458,  th)  is  very  large  and  long,  while  the  thyroid  (t)  is 
a  small,  oval  mass  situated  at  the  beginning  of  the  bronchi. 

The  following  account  and  drawings  of  the  anatomy  of 
the  pigeon  have  been  prepared  from  original  dissections  by 
Dr.  C.  S.  Minot.  As  pigeons  are  one  of  the  most  readily 
obtainable  and  convenient  types  of  birds,  the  following 
description  of  the  anatomy  of  a  male  is  given  as  illustrative 
of  the  class,  those  peculiarities  being  especially  noticed  by 
which  birds  are  distinguished  from  reptiles  and  mammals. 

Before  dissecting  a  bird,  it  must  be  carefully  plucked  ; 
this  operation  is  much  facilitated  by  dipping  the  animal  in 
boiling  water  for  a  few  minutes.  The  limbs  and  muscles  of 
one,  best  of  the  left,  side  are  to  be  removed  ;  the  powerful 
pectoral  muscles  cut  off  close  to  their  attachment  to  the 
keel  of  the  breast-bone,  and  the  ribs  then  cut  away,  care 
being  taken  to  avoid  injuring  any  of  the  internal  organs, 
most  of  which  will  now  be  displayed  in  situ  nearly  as  shown 
in  Fig.  459,  which  represents  a  dissection  carried  somewhat 
further. 

The  skin  (Fig.  459,  E,  from  the  neck)  is  characterized  by 
the  presence  of  numerous  ridges  which  cross  one  another, 
so  as  to  enclose  quadrilateral  spaces  ;  at  the  intersections 
of  the  ridges  are  small  pits  in  which  the  feathers  are  in- 
serted. 

The  digestive  canal  begins  in  the  horny  bill  with  three 
openings,  one  the  large  gape  or  mouth,  and  two  oblique 
elongated  nasal  clefts  (n),  through  which  respiration  is  or- 
dinarily alone  effected.  It  then  extends  backward  under- 
neath the  base  of  the  skull,  where  it  splits  into  the  oesopha- 
gus and  trachea,  two  large  tubes  which  run  down  the  front 
of  the  neck,  the  oesophagus  on  the  right  and  the  trachea 
on  the  left.  Just  below  the  head  the  trachea  lies,  in  its 
normal  position,  in  front  of  the  oesophagus,  though  in  most 


526  ZOOLOGY. 

adult  birds  both  tubes  follow  a  symmetrical  course,  but  ex- 
hibit a  mock  or  secondary  symmetry  with  regard  to  each 
other.  The  origin  of  the  two  canals  is  embraced  by  the 
hyoidean  apparatus,  one  of  the  horns  (cornua)  of  which  ap- 
pears at  Hy ;  the  apparatus  is  too  complicated  to  be  de- 
scribed here  ;  it  closely  resembles  that  of  reptiles,  and  is 
functionally  connected  with  the  rapid  thrusting  out  of  the 
tongue.  In  some  birds,  as,  for  example,  the  woodpeckers 
and  humming-birds,  the  horns  are  so  developed  as  to  curve 
round  the  back  of  the  cranium  on  to  the  top  of  the  skull. 
(Fig.  474). 

The  trachea  (TV)  is  composed  of  cartilaginous  rings  with 
intervening  membranes,  and  an  external  sheath  of  connect- 
ive tissue,  which  has  been  removed  at  Tr.  It  extends  into 
the  thorax,  and  is  of  nearly  uniform  diameter  throughout, 
except  at  its  lower  extremity,  where,  as  shown  in  Fig.  459, 
D,  it  forms  an  enlargement,  the  syrinx  or  vocal  chamber 
( L),  found  only  in  birds,  but  wanting  in  the  ostrich,  etc. 
(RatitcB),  storks,  and  certain  birds  of  prey.  The  trachea 
terminates  immediately  behind  the  syrinx  in  two  smaller 
branches,  the  bronchi  (E)9  each  of  which  passes  into  the 
lung  (Lu)  of  the  same  side.  The  cartilaginous  rings  of 
the  bronchi  are  incomplete,  the  walls  being  partly  formed 
by  an  elastic  membrane.  The  rings  of  the  trachea  are  pe- 
culiarly modified  in  the  syrinx,  which  is  furnished  with  ex- 
ternal muscles  and  internal  membranous  expansions,  serving 
to  produce  the  voice  ;  the  muscles  are  the  sterno-tracheal, 
furculo-  or  claviculo-tracheal,  and  the  proper  muscles  of  the 
syrinx.  A  true  larynx  is  present  in  the  upper  part  of  the 
trachea,  but  is  unessential  to  the  formation  of  the  voice. 
The  trachea  presents  flexuosities  in  various  birds,  usually 
more  marked  in  the  male  than  in  the  female  ;  in  swans  there 
is  a  great  band  which  extends  into  the  hollow  breast-bone, 
but  the  object  of  this  disposition  is  unknown. 

The  lungs  (Fig.  459,  Lu)  are  two  large  sacs,  placed  dor- 
sally  in  the  anterior  part  of  the  body-cavity,  but  not  suspend- 
ed freely  in  a  short  thoracic  sac  nor  enclosed  in  a  pleura,  as 
in  mammals  ;  they  are  composed  of  reddish  spongy  tissues, 
and  are  attached  between  the  ribs  by  connective  tissue. 


ANATOMY  OF  THE  PIGEON.  527 

Each  lung  has  upon  its  outer  and  dorsal  surface  five'  trans- 
verse depressions,  corresponding  to  as  many  ribs.  The 
bronchi  and  pulmonary  blood-vessels  enter  together  the 
anterior  third  of  the  lungs,  and  follow  one  another  in  their 
ramifications,  but  the  bronchus  traverses  the  lungs,  giving 
off  numerous  branches,  and  opens  into  the  abdominal  air- 
sac,  while  upon  the  surface  of  the  lungs  there  are  small 
openings  communicating  with  the  remaining  air-sacs. 
These  structures  the  student  had  best  tear  through  and 
altogether  neglect  in  his  first  dissection.  The  air-sacs  are 
thin-walled  bags,  nine  in  number  :  three  near  the  clavicle, 
four  in  the  thorax,  and  two  in  the  abdomen  ;  their  ramifi- 
cations extend  even  into  the  bones,  most  of  which  are  ac- 
cordingly found  to  be  hollow.  This  striking  organization 
is  one  of  the  most  characteristic  peculiarities  of  birds,  and 
serves  to  lighten  the  body  by  filling  large  spaces  with  warm 
air,  besides  fulfilling  certain  other  less  obvious  functions. 
In  many  chameleons  and  some  Geckos  the  lungs  have  di- 
verticula  or  offshoots,  which  foreshadow  the  air-sacs  of 
birds. 

The  alimentary  canal  consists  of  seven  parts  :  the  oes- 
ophagus, crop,  glandular  and  muscular  stomachs,  large  and 
small  intestines,  and  cloaca.  The  oesophagus  extends  about 
three  fifths  of  the  way  down  the  right  side  of  the  neck,  and 
is  approximately  of  the  same  diameter  as  the  trachea,  with 
regard  to  which,  as  before  mentioned,  it  lies  symmetrically. 
It  opens  into  the  crop  (Cr],  a  thin-walled  sac,  which  fills 
the  triangular  space  between  the  base  of  the  neck  and  the 
keel  of  the  sternum,  and  forms  a  large  part  of  the  curved 
outline  of  the  breast.  In  the  specimen  figured,  the  left  half 
of  the  crop  has  been  removed  to  show  the  irregular  folds 
upon  the  inner  surface,  the  deep  lateral  pouch  and  the 
three  posterior  longitudinal  folds  of  one  side,  which  serve 
to  guide  the  food  onward  to  the  stomach.  As  shown  in 
Fig.  459,  D,  the  crop  (Cr)  ends  just  to  the  right  of  and 
above  the  trachea,  in  a  dorsally-placed,  narrow  tube,  that 
reaches  to  the  origin  of  the  bronchi,  and  there  gradually  ex- 
pands into  the  glandular  stomach,  which  cannot,  however, 
be  seen  in  a  general  dissection,  while  the  heart,  lungs,  and 


528  ZOOLOGY. 

liver  are  still  in  situ.  The  muscular  stomach  or  gizzard 
(St)  of  the  main  figure  is  represented  very  large,  being 
distended  with  food  ;  it  is  sometimes  found  much  con- 
tracted ;  it  is  not  sharply  separated  from  the  glandular 
stomach,  the  two  being  in  reality  only  the  greatly  modified 
anterior  and  posterior  divisions  of  the  same  dilatation.  The 
opening  of  the  glandular  stomach  and  the  origin  of  the 
small  intestine  are  near  together  upon  the  anterior  border 
of  the  gizzard.  The  walls  of  this  last  organ  are  remarkable 
for  the  enormous  development  of  the  muscular  layers, 
especially  in  the  graminivorous  birds,  under  which  pigeons 
are  to  be  included  ;  the  muscles  radiate  on  each  side  from 
a  central  tendinous  space.  The  small  intestine  has  nu- 
merous coils,  in  the  first  of  which  lies  the  pancreas  (Pan), 
very  much  as  in  mammals.  The  large  intestine  (R)  is  rel- 
atively short ;  its  commencement  is  marked  by  two  small 
diverticula,  distinctive  of  birds.*  These  appendages  are 
well  developed  in  some  species,  as,  for  instance,  the  Galli- 
nacem,  while  in  the  bustard  they  have  been  described  as 
three  feet  long.  Gegenbaur  considers  the  oesophagus,  crop, 
and  stomach  to  be  derived  from  the  fore-gut,  the  small  in- 
testine from  the  mid-gut,  and  the  large  intestine  from  the 
hind-gut  of  the  embryo.  The  cloaca  (Cl)  is  the  short  and 
widened  termination  of  the  alimentary  canal,  and  further 
receives  four  ducts,  the  two  ureters  ( Ur),  and  in  the  male 
the  two  vasa  deferentia  ( Vd),  in  the  female  the  two  ovi- 
ducts. 

The  digestive  canal  has  two  glandular  appendages,  the 
pancreas  (Pan)  and  the  liver  (Li)  ;  the  former,  as  in 
birds  generally,  is  quite  large,  whitish,  and  sends  out  a  pro- 
longation, which  extends  to  the  spleen  ;  it  has  two  ducts. 
The  liver  (Li)  is  very  voluminous,  dark  reddish  brown  in 
color,  and  forms  two  lobes,  which  rest  upon  the  apex  of  the 
heart  and  the  gizzard,  and  conceal  the  glandular  stomach. 
There  is  no  gall-bladder,  a  somewhat  unusual  feature  among 
birds,  but  there  are  two  bile-ducts,  the  larger  and  shorter 

*  Some  snakes  have  a  single  diverticulum,  as  is  said  to  be  the  case 
with  herons. 


ANATOMY  OF  THE  PIGEON.  529 

opening  into  the  upper  part,  while  the  longer  duct,  after 
uniting  with  that  of  the  pancreas,  opens  into  the  lower  part 
of  the  duodenum. 

The  length  of  the  neck  in  birds  is  never  less  than  the 
height  at  which  the  body  is  carried  from  the  ground  ;  the 
number  of  vertebrae  entering  into  its  formation  varies  from 
9  to  24  (swan) ;  in  the  pigeon  there  are  twelve,  accompanied 
by  a  corresponding  number  of  spinal  nerves,  the  branches  of 
which  may  be  observed  immediately  underneath  the  skin. 
The  main  mass  of  the  neck  is  composed  of  the  vertebral  col- 
umn and  muscles,  the  trachea  and  oesophagus.  On  either 
side  of  the  base  of  the  neck,  in  close  proximity  to  the  trachea 
and  carotid  artery,  is  a  small  oval  white  body,  the  thyroid 
gland  (Tr),  at  first  developed  as  an  evagination  of  the  fore- 
gut,  but  afterward  becoming  a  closed  and  ductless  sac, 
which  is  found  in  the  majority  of  vertebrates,  but  the  use  of 
which  to  the  organism  is  entirely  unknown.  Above  the  thy- 
roid lie  the  carotid  artery  and  jugular  vein,  the  main  vas- 
cular trunks  of  the  head  and  neck.  The  right  jugular  vein 
is  usually  the  largest.  Along  the  side  of  the  neck,  above 
the  trachea  on  the  left  and  the  oesophagus  on  the  right,  lies 
the  elongated  thymus  gland  (Tm),  drawn  somewhat  dia- 
grammatically  ;  this  gland  forms  part  of  the  lymphatic  sys- 
tem, and  in  minute  structure  resembles  the  spleen. 

The  heart  (Ht)  lies  immediately  below  the  lungs  and 
against  the  sternum,  with  its  apex  between  the  two  lobes  of 
the  liver  pointing  obliquely  downward  and  backward  ;  it 
is  enclosed  in  a  thin  membranous  bag,  the  pericardium, 
which  is  filled  with  serous  fluid  and  attached  to  the  roots  of 
the  main  vascular  trunks.  To  study  the  heart,  it  must  be 
excised,  taking  the  greatest  care  to  leave  as  much  as  possible 
of  the  vessels,  especially  the  large  veins  behind,  in  connec- 
tion with  it.  Viewed  from  behind  (Fig.  459,  (?),  the  heart 
is  seen  to  be  composed  of  four  chambers,  the  two  anterior 
ones,  the  auricles,  being  the  smaller.  The  left  auricle  receives 
upon  its  dorsal  side  the  opening  of  the  united  pulmonary 
veins  (Pv),  one  from  each  lung  ;  the  right  auricle  is  larger 
than  the  left,  and  receives  in  its  upper  portion  the  right  vena 
cava  superior  ( Vsd)  ;  in  its  lower  portion  the  left  vena 


530  ZOOLOGY. 

cava  superior  ( Vs),  just  above  which  opens  the  vena  cava 
inferior  ( Vi).  The  two  larger  and  posterior  chambers,  the 
ventricles,  form  the  apex  of  the  heart,  and  give  off  the 
arterial  trunks.  Of  the  ventricles,  the  left  ( Yen.  s)  is  the 
largest,  has  the  thickest  walls,  and  alone  extends  to  the  apex 
of  the  heart ;  it  gives  off  the  aorta,  a  short  trunk  which 
divides  into  a  right  and  left  branch,  from  which  spring  the 
carotid  arteries  for  the  head  and  neck,  and  which  continue 
as  the  subclavian  or  auxiliary  -arteries  A  and  A'  for  the 
wings.  From  the  base  of  the  right  branch  A  arises  the 
large  aorta  (Ao),  which  turns  around  the  bronchus  of  the 
same  side,  and  runs  to  the  front  and  right  of  the  vertebral 
column  through  the  abdomen,  forming  the  descending  aorta 
which  gives  off  arteries  to  the  intercostal  and  lumbar  regions 
and  to  the  viscera,  and  terminates  in  a  crural  branch  to  each 
leg.  The  right  ventricle  ( Ven.  d)  has  much  thinner  walls 
than  the  left ;  from  it  arises  the  pulmonary  aorta  (Pa) 
which  soon  branches  to  each  side. 

Birds  are  distinguished  from  reptiles  by  having  a  four- 
chambered  heart  and  a  single  permanent  aortic  trunk  ; 
from  mammals  by  the  persistence  of  the  right  instead  of 
the  left  aortic  arch  to  form  the  aorta.  Each  auricle  com- 
municates with  the  ventricle  of  the  same  side  ;  the  con- 
necting orifices  are  furnished  with  valves.  The  right 
auriculo- ventricular  valve  is  muscular  in  all  birds,  while 
the  left  is  membranous. 

The  uro-genital  organs  lie  dorsally  in  the  hinder  part  of 
the  body-cavity.  The  dark  reddish  brown  kidneys  (Ki] 
consist,  as  in  most  birds,  each  of  three  lobes,  the  posterior 
being  the  largest ;  they  lie  immediately  behind  the  lungs. 
The  ureters  (Ur)  are  slightly  curved,  whitish  tubes,  which 
pass  back  from  the  kidneys  and  open  into  the  dorsal  side  of 
the  cloaca.  The  testicles  (Te)  are  two  large  oval  whitish 
bodies,  each  situated  immediately  behind  the  lung  and  be- 
low the  kidney  of  the  same  side.  The  vasa  deferentia  (  Yd) 
arise  from  the  anterior  and  inner  surfaces  of  the  testicles, 
have  a  flexuous  course,  and,  after  forming  terminal  enlarge- 
ments, open  separately  into  the  cloaca,  in  front  of  the 


ANATOMY  OF  THE  PIGEON.  531 

ureters.     In  neither  sex  in  birds  are  the  genital  ducts  pro- 
vided with  accessory  glands. 

As  usual  among  birds,  the  head  is  approximately  top- 
shaped.  The  eyes  are  very  large  and  much  exposed,  as  be- 
comes evident  upon  dissecting  off  the  skin  as  in  the  figure. 
The  external  ear  is  a  mere  circular  opening,  entirely  covered 
during  life  by  the  feathers.  The  side  of  the  cranium  may 
be  removed  so  as  to  expose  the  brain,  with  the  large  smooth 
cerebral  hemispheres  (C),  the  convoluted  cerebellum  (Cb), 
and  the  much  smaller  medulla  (Md).  To  study  the  brain 
satisfactorily,  it  must  be  removed  from  its  case.  A  view  of 
it  from  the  side  is  given  in  Fig.  459,  A,  and  a  view  from 
above  in  the  same  figure  at  B.  The  medulla  oUongata 
(M)  appears  as  hardly  more  than  the  enlarged  upper  end 
of  the  spinal  cord  ;  upon  its  dorsal  surface  there  is  a  trian- 
gular depression  IV,  the  fourth  ventricle,  which  is  par- 
tially concealed  by  the  cerebellum.  (Cb),  a  large  mass  mark- 
ed by  transverse  ridges  and  imperfectly  divided  into  three 
lobes,  thus  exhibiting,  both  in  its  size  and  its  complication 
of  structure,  a  great  advance  over  the  reptiles.  The  corpora 
quadrigemina  or  Mgemina*  (Q)  project  as  two  large  lobes  far 
out  on  the  sides  and  down  the  base  of  the  brain  ;  their  posi- 
tion and  great  size  are  characteristic  for  the  whole  class. 
The  optic  thalami,  which  intervene  between  the  bigemina 
and  the  hemispheres,  are  relatively  small ;  they  enclose  the 
third  ventricle  and  have  a  funnel-shaped  downward  exten- 
sion, to  which  the  pituitary  body  is  attached,  as  to  a  stalk. 
The  cerebral  hemispheres  (He)  form  more  than  half  of  the 
whole  brain  ;  their  surfaces  are  entirely  without  convolu- 
tions, but  each  hemisphere  has  a  small  projection,  the  olfac- 
tory lobe  (01),  upon  its  anterior  and  inferior  extremity. 
The  cavities  of  the  hemispheres  or  the  lateral  ventricles  are 
very  large  and  extend  also  into  the  olfactory  lobes.  The 
greatly  thickened  inferior  walls  of  the  hemispheres  are 
termed  the  corpora  stridta.  Birds  differ  from  mammals  in 
having  only  a  rudimentary  fornix  and  no  corpus  callosum. 
The  description  of  the  cranial  nerves  is  purposely  omitted. 

*  Also  called  the  optic  lobes,  middle  brain,  and  mesencephalon. 


532  ZOOLOGY. 

Between  the  liver  and  the  glandular  stomach  lies  the 
small,  somewhat  elongated,  reddish  brown  spleen. 

In  birds,  as  in  most  vertebrates,  several  spinal  nerves  unite 
to  form  a  brachial  plexus,  part  of  which  is  shown  at  B,  and 
which  supplies  the  wings.  Posteriorly,  there  is  also  formed 
a  plexus,  the  lumbar,  for  the  legs. 

The  muscles  of  the  limbs  are  much  modified  in  accordance 
with  the  peculiar  locomotion  of  birds.  In  connection  with 
the  power  of  flight,  the  sternum  has  a  very  large  keel,  to 
which  are  attached  the  pectoral  muscles.  The  pectoralis 
major  (Pe)  is  the  most  external ;  it  arises  from  the  outer 
half  of  the  keel  and  is  inserted  into  the  humerus,  and  effects 
the  downward  stroke  of  the  wing.  The  second  pectoral 
(pectoralis  tertius  of  some  authors  and  the  homologue  of 
the  comparatively  insignificant  subclavius  of  human  anat- 
omy) arises  from  the  inner  portion  of  the  keel,  runs  forward 
and  outward,  and,  tapering  off,  passes  through  a  groove  be- 
tween the  coracoid  and  sternum,  as  over  a  pulley,  to  be  in- 
serted into  the  humerus.  The  wing  is  raised  by  its  action. 
In  the  ostrich,  etc.  (RatitcB),  the  breast-bone  has  no  keel, 
and  the  disposition  of  the  muscles  of  the  rudimentary  wings 
therefore  differs  greatly  from  that  here  described.  (Minot.) 

The  ovary  may  be  distinguished  by  the  large  incipient  eggs 
forming  the  greater  part  of  the  mass.  The  right  ovary  is 
usually  undeveloped,  but  when  partly  formed,  as  in  some 
hawks,  the  eggs  do  not  mature. 

The  "  white"  is  deposited  around  the  true  egg  in  the  upper 
part  of  the  oviduct,  while  the  shell  is  secreted  from  glands 
emptying  into  the  lower  part  of  the  duct.  The  eggs  of 
birds  are  enormous  in  proportion  to  those  of  other  verte- 
brate animals,  except  the  lizards.  The  egg  of  the  JSpyornis, 
an  extinct  bird  of  Madagascar,  is  about  a  third  of  a  metre 
(13£  inches)  in  length,  and  as  the  egg  is  in  reality  a  cell, 
this  is  the  largest  cell  known.  The  development  of  the 
chick  is  better  known  than  that  of  any  other  animal.  It 
travels  the  same  developmental  path  as  other  vertebrates  in 
which  an  amnion  and  allantois  are  formed.  About  the  sixth 
day  of  embryonic  life  the  bird-characters  begin  to  appear, 
the  wings  begin  to  differ  from  the  legs,  the  crop  and  giz- 


ANATOMY  OF  THE  PIGEON. 


533 


534  ZOOLOGY. 

zard  are  indicated,  and  the  beak  begins  to  develop.  By  the 
ninth  or  tenth  day  the  feathers  originate  in  sacs  in  the 
skin,  these  sacs  by  the  eleventh  day  appearing  to  the  naked 
eye  as  feathers  ;  the  nails  and  scales  of  the  legs  and  toes  are 
marked  out  on  the  thirteenth  day,  and  by  this  time  the 
cartilaginous  skeleton  is  completed,  though  the  deposition 
of  lime  (ossification)  begins  on  the  eighth  or  ninth  day  by 
small  deposits  of  bone  in  the  shoulder-blade  and  limb-bones  ; 
centres  of  ossification  appearing  in  the  head  by  the  thir- 
teenth day. 

"  After  the  sixth  day,  muscular  movements  of  the  embryo 
probably  begin,  but  they  are  slight  until  the  fourteenth  day, 
when  the  embryo  chick  changes  its  position,  lying  length- 
ways in  the  egg,  with  its  beak  touching  the  chorion  and 
shell  membrane,  where  they  form  the  inner  wall  of  the 
rapidly  increasing  air-chamber  at  the  broad  end.  On  the 
twentieth  day  or  thereabouts,  the  beak  is  thrust  through 
these  membranes,  and  the  bird  begins  to  breathe  the  air 
contained  in  the  chamber.  Thereupon  the  pulmonary  cir- 
culation becomes  functionally  active,  and  at  the  same  time 
blood  ceases  to  flow  through  the  umbilical  arteries.  The 
allantois  shrivels  up,  the  umbilicus  becomes  completely 
closed,  and  the  chick,  piercing  the  shell  at  the  broad  end 
of  the  egg  with  repeated  blows  of  its  beak,  casts  off  the 
dried  remains  of  allantois,  amnion,  and  chorion,  and  steps 
out  into  the  world."  (Foster  and  Balfour.) 

Some  young  birds  haye,  as  in  turtles  and  snakes,  a  tem- 
porary horny  knob  on  the  upper  jaw,  used  to  crack  the 
shell  before  hatching.  In  birds  which  lay  small  eggs,  with 
a  comparatively  small  yolk,  the  young  are  brooded  in  nests 
and  fed  by  the  parent ;  but  in  the  hen  and  other  gallina- 
ceous birds,  in  the  wading  birds  and  many  swimmers,  as 
dufcks,  where  the  yolk  is  more  abundant,  the  young  main- 
tain themselves  directly  on  hatching. 

Following  the  business  of  reproduction  is  the  process  of 
moulting  the  old  and  weather-beaten  feathers.  This  is  often 
a  critical  period  in  a  bird's  life,  judging  by  the  occasional 
mortality  among  domesticated  and  pet  birds.  The  annual 
moulting  begins  at  the  close  of  the  breeding  season,  though 


SONGS  OF  BIRDS.  535 

some  birds  monlt  twice  and  thrice.  The  quill-feathers  (rem- 
iges)  are  usually  shed  in  pairs,  but  in  the  ducks  (Anatidce) 
they  are  shed  at  once,  so  that  these  birds  do  not  at  this 
time  go  on  the  wing,  while  the  males  put  off  the  highly- 
colored  plumage  of  the  days  of  their  courtship,  and  as- 
sume for  several  weeks  a  dull  attire.  In  the  ptarmigan 
both  sexes  not  only  moult  after  'the  breeding  season  is 
over  into  a  gray  suit,  and  then  don  a  white  winter  suit, 
but  also  wear  a  third  dress  in  the  spring.  In  the  northern 
hemisphere  the  males  of  many  birds  put  on  in  spring 
bright,  gay  colors.  Other  parts  are  also  shed  ;  for  example, 
the  thin,  horny  crests  on  the  beak  of  a  western  pelican  (Peli- 
canus  erytlirorliynchus),  after  the  breeding  season,  are  shed 
like  the  horns  from  the  head  of  deer.  Even  the  whole 
covering  of  the  beak  and  other  horny  parts,  like  those 
about  the  eyes  of  the  puffin,  may  also  be  regularly  shed. 
The  variations  in  the  frequency,  duration,  and  completeness 
of  the  process  are  endless. 

As  a  rule,  male  birds  are  larger  and  have  brighter  col- 
ors, with  larger  and  more  showy  combs  and  wattles  than 
the  females,  as  seen  in  the  domestic  cock  and  hen  ;  and  the 
ornamentation  is  largely  confined  to  the  head  and  the  tail, 
as  seen  especially  in  male  humming-birds.  Mr.  Darwin  has 
adduced  a  multitude  of  examples  in  his  Descent  of  Man, 
Vol.  2.  Sometimes,  however,  both  sexes  are  equally  orna- 
mented, and  in  rare  cases  the  female  is  more  highly  colored 
than  the  male;  she  is  sometimes  also  larger,  as  in  most  birds 
of  prey.  There  is  little  doubt  that  the  bright  colors  of  male 
birds  render  them  more  conspicuous  and  to  be  more  readily 
chosen  by  the  females  as  mates,  for  in  birds,  as  in  higher 
animals,  the  female  may  show  a  preference  for  or  antipathy 
against  certain  males.  Indeed,  as  Darwin  remarks,  when- 
ever the  sexes  of  birds  differ  in  beauty,  in  the  power  of  sing- 
ing, or  in  producing  what  he  calls  "  instrumental  music/' 
it  is  almost  invariably  the  male  which  excels  the  female. 

The  songs  of  birds  are  doubtless  in  part  sexual  calls  or 
love-notes,  though  birds  also  sing  for  pleasure.  The  notes  of 
birds  express  their  emotions  of  joy  or  alarm,  and  in  some 
cases  at  least  the  notes  of  birds  seem  to  convey  intelligence 


536  ZOOLOGY. 

of  the  discovery  of  food  to  their  young  or  their  mates.  They 
have  an  ear  for  music  ;  some  species,  as  the  mocking-bird, 
will  imitate  the  notes  of  other  birds.  The  songs  of  birds 
can  be  set  to  music.  Mr.  X.  Clark  has  published  in  the 
American  Naturalist  (Vol.  13,  p.  21)  the  songs  of  a  number 
of  our  birds.  The  singular  antics,  dances,  mid-air  evolu- 
tions, struts,  and  posturings  of  different  birds,  are  without 
doubt  the  visible  signs  of  emotions  which  in  other  birds  find 
vent  in  vocal  music. 

The  nesting  habits  of  birds  are  varied.  Many  birds,  as 
the  gulls,  auks,  etc.,  drop  their  eggs  on  bare  ground  or  rocks  ; 
as  extremes  in  the  series  are  the  elaborate  nests  of  the 
tailor-bird,  and  the  hanging  nest  of  the  Baltimore  oriole, 
while  the  woodpecker  excavates  holes  in  dead  trees.  As  a 
rule,  birds  build  their  nests  concealed  from  sight  ;  in  tropi- 
cal forests  they  hang  them,  in  some  cases,  out  of  reach  of  pred- 
atory monkeys  and  reptiles.  Birds  may  change  their  nesting 
habits  sufficiently  to  prove  that  they  have  enough  reasoning 
powers  to  meet  the  exigencies  of  their  life.  Parasitic  birds, 
like  the  cuckoo  and  cow-birds,  lay  their  eggs  by  stealth  in 
the  nests  of  other  birds. 

The  duties  of  incubation  are,  as  a  rule,  performed  by  the 
female,  but  in  most  Passerine  birds  and  certain  species  of 
other  groups,  the  males  divide  the  work  with  the  females, 
and  in  the  ostrich  and  other  Ratitce  the  labor  is  wholly  per- 
formed by  the  males. 

There  are  probably  from  7000  to  8000  species  of  living 
birds;  Gray's  "Handlist"  enumerates  11,162,  but  many 
of  these  are  not  good  species.  Of  the  whole  number,  about 
700  distinct  species  or  well-marked  geographical  races  in- 
habit North  America  north  of  Mexico.  The  geographical 
distribution  of  birds  is  somewhat  complicated  by  their  mi- 
grations. While  the  larger  number  of  species  are  tropical, 
arctic  birds  are  abundant,  though  most  of  them  are  aquatic. 
In  the  United  States  there  are  three  centres  of  distribution  : 
(1)  the  Atlantic  States  and  Mississippi  Valley  ;  (2)  the 
Rocky  Mountain  plateau,  and  (3)  the  Pacific  coast.  The 
migrations  of  birds  will  be  treated  of  near  the  close  of  this 
volume. 


FOSSIL  BIRDS. 


537 


While  in  former  times  existing  birds  were  divided  into  a 
large  number  of  "  orders,"  these  are  now  known  to  be  sub- 
divisions of  the  two  sub-classes  Ratitce  and  Oarinaim,  and 
probably  in  many  cases  should  be  honored  only  with  the  rank 
of  sub-orders.  The  discovery  of  the  Arclmopteryx  and  of 
birds  with  teeth  and  biconcave  vertebra?  has  essentially  mod- 
ified prevailing  views  as  to  the  classification  of  birds. 

Sub-class  1.  Saururce. — The  oldest  bird,  geologically 
speaking,  is  the  Arclmopteryx  (Fig.  460)  of  the  Jurassic 
slates  of  Solenhofen,  Germany.  This  was  a  bird  about  the 
size  of  a  crow,  the  tail  being  22  cent.  (8-9  inches)  long,  but 
longer  than  the  body,  supported  by  many  movable  vertebrae 


Fig.  460.— Restoration  of  Archceopteryx  macrura.—  After  Owen,  from  Nicholson. 

and  covered  with  feathers  in  distichous  series,  not  in  the 
shape  of  a  fan.  The  jaw-bones  were  long,  and  contained 
conical  teeth.  The  head,  shoulder  girdle,  and  fore  limbs, 
with  their  three  digits,  were  reptilian  in  form.  (Vogt.)  In 
these  respects  and  in  the  long  tail  the  creature  served  as  a 
connecting  link  between  the  reptiles,  such  as  the  bird-like 
Comp8ognathu8,a,nd  the  existing  birds.  The  hind  legs  and 
wings  have  the  ordinary  bird  structure,  though  the  metacar- 
pal  bones  were  not  co-ossified;  the  foot  consisted  of  three  digits. 
Sub-class  %.  Odontornithes. — Still  another  connecting  link 
between  the  reptiles  and  birds  has  been  discovered  by  Marsh 


538  ZOOLOGY. 

in  the  upper  Cretaceous  beds  of  this  country.  The  remains 
of  Ichthyornis  indicate  an  aquatic  bird  about  the  size  of  a 
pigeon.  The  reptilian  affinities  are  seen  in  the  vertebrae, 
which,  unlike  those  of  all  other  birds,  are  biconcave,  and  in 
the  long,  slender  jaws,  with  stout,  conical  teeth  held  in 
sockets,  as  in  the  crocodiles.  On  the  other  hand,  the  wings 
were  well  developed,  and  the  legs  were  of  the  ordinary  bird 
type,  the  metacarpal  bones  being  co-ossified,  while  ,the  ster- 
num was  keeled.  In  a  second  member  of  the  group  (Hes- 
perornis)  the  teeth  were  in  grooves,  the  vertebrae  as  in  recent 
birds,  the  sternum  without  a  keel,  and  the  wings  were  rudi- 
mentary (Marsh). 

Sub-class  3.  Ratitcs. — This  group,  represented  by  the  kiwi- 
kiwi,  the  moa,  cassowary,  and  ostrich,  is  characterized  by 
the  smooth  unkeeled  sternum  and  the  short  tail  ;  the  wings 
are  rudimentary  and  the  hind  legs  strong,  these  birds  (except 
Apteryx}  being  runners,  and  either  of  large  or,  as  in  the 
extinct  forms,  of  colossal  size. 

The  simplest  form  is  the  "  kiwi-kiwi,"  or  Apteryx  of 
New  Zealand  (Fig.  461),  of  which  there  are  three  or  four 
species.  It  is  of  the  size  of  a  hen,  with  a  long  slender  beak, 
the  nostrils  situated  at  the  end  of  the  upper  jaw,  while  the 
body  is  covered  with  long  hairy  feathers.  The  female  lays 
only  a  single  large  egg,  which  weighs  one  quarter  as  much  as 
the  bird  itself,  in  a  hole  in  the  ground.  It  is  a  night  bird, 
hiding  by  day  under  trees. 

The  giant,  ostrich-like,  extinct  birds  of  New  Zealand, 
called  moa,  and  represented  by  several  species,  chiefly  of 
the  genera  Dinornis  and  Palapteryx  (Fig.  461),  were  sup- 
posed to  have  been  contemporaries  of  the  Maoris  or  natives 
of  New  Zealand.  While  a  fourth  toe  (hallux)  is  present  in 
the  Apteryx,  the  moa-bird  has  only  three  toes. 

The  largest  of  the  moas,  Dinornis  giganteus  of  Owen, 
stood  nearly  three  metres  (9£  feet)  in  height,  the  tibia  or 
shin-bone  alone  measuring  nearly  a  metre  (2  feet  10  inches) 
in  length.  These  moa  birds  belong  to  three  genera  :  Di- 
nornis with  ten,  Palapteryx  with  three,  and  Aptornis  with 
a  single  species. 

Allied  to  the  moa  was  a  still  larger  bird,  the  JEpyornis 

• 


CURSORIAL   BIRDS. 


539 


maximus,  of  Madagascar,  supposed  by  some  to  be  the  roc 
of  the  Arabian  Nights'  Tales.  Of  this  colossal  bird,  remains 
of  the  skull,  some  vertebrae,  and  a  tibia  64  cent,  long,  have 
been  found.  The  single  egg  discovered  is  of  the  capacity  of 
one  hundred  and  fifty  hens'  eggs. 

To  this   order  belong  the  three-toed  cassowaries  of  the 
East  Indies  and  Australia,  and  the  emeu  of  Australia  ;  both 


Fig.  461.— Moa,  Palapteryx,  with  three  Kiwi-kiwi  birds.— After  Hochstetter,  from 
Tenney's  Zoology. 

of  these  birds  are  about  2  metres  (5-7  feet)  high.  The 
South  American  ostrich  ( RJiea  A mericana)  with  three  toes  to 
each  foot,  is  a  smaller  bird,  standing  1-3  metres  high,  run- 
ning in  small  herds  on  the  pampas.  The  two-toed  ostrich 
(8truthio  camelus  Linn.),  of  the  deserts  of  Africa  and 
Arabia,  now  reared  for  the  feathers  of  its  wings  and  tail,  so 


540  ZOOLOGY. 

valuable  as  articles  of  commerce,  is  the  largest  bird  now  liv- 
ing, being  2-2-7  metres  (6-8  feet)  high.  It  can  outrun  a 
horse,  and  lives  in  flocks.  It  lays  about  thirty  large  white 
eggs  in  a  nest  in  the  sand  ;  they  are  covered  in  the  day- 
time by  the  hen  or  left  exposed  to  the  sun,  while  at  night 
the  male  sits  over  and  guards  them.  In  Cape  Colony,  os- 
trich-culture has  become  an  important  business  ;  in  1865 


a! 


Fig.  462.— Great  Auk.— From  Coucs'  Key. 

there  were  only  eighty  individuals  on  the  ostrich  farms  ;  in 
1875  there  were  32,247  ostriches,  either  free  or  in  parks 
where  Lucerne  grass  is  cultivated  as  food  for  these  useful 
birds.  The  South  American  ostrich  is  in  Patagonia  hunted 
for  its  feathers.  During  the  Eocene  Tertiary  period  a  gi- 
gantic ostrich-like  bird  (Diatryma  Cope),  twice  as  large  as 


DIVING  BIRDS.  541 

an  ostrich,  lived  in  Texas  and  New  Mexico,  part  of  a  leg- 
bone  having  been  found  on  the  San  Juan  River. 

Sub-class  4.  CarinatcB. — All  other  living  birds  belong  to 
this  group  ;  they  are  remarkably  homogeneous  in  form 
and  structure,  and  the  subdivisions  may  be  regarded  as 
orders.  They  are  characterized  by  the  keeled  breast-bone 
or  sternum — the  wings,  as  a  rule,  being  well  developed. 

The  diving  birds  (Pygopodes)  are  eminent  as  swimmers, 
and  comprise  the  penguins,  auks,  puffins,  grebes,  and  loons. 
The  penguins  are  confined  to  the  antarctic  regions.  They 
are  large  birds,  and  form  a  characteristic  element  in  a  Pata- 
gonian  landscape.  The  bones  are  solid,  not  light  and  hol- 
low, as  in  other  birds  ;  the  wings  are  small,  paddle-like, 
with  scale-like  feathers  ;  on  shore  they  have  an  awkward 
gait.  They  lay  but  a  single  egg,  and  some  species  do  not 
lay  their  egg  on  the  rocks,  but  bear  it  about  in  a  pouch- 
like  abdominal  fold.  The  penguins,  however,  differ  so 
much  from  the  other  divers  that  they  are  now  often  ranked 
as  a  separate  group  of  this  grade,  called  Sphenisci. 

The  guillemots  and  auks  are  characteristic  arctic  birds 
ranging  from  Labrador  northward,  and  have  great  powers 
of  flight.  The  gare  fowl,  or  great 
auk  (Alca  impennis,  Fig.  462),  is 
nearly  or  quite  extinct,  being  un- 
til lately  confined  to  one  or  two 
inaccessible  islets  near  Iceland, 
where  it  has  been  extinct  since 
1844,  and  to  Labrador,  though 
formerly  it  ranged  from  Cape 
Cod  northward,  a  few  survivors 
having  lived  on  the  Funks,  an 
islet  on  the  eastern  coasfc  of  New- 
foundland, within  perhaps  thirty 
years. 

The   loons    are  Well   known  for       Fig.    463.—  Roseate    Tern.— From 
1 1      •     i  •  -I  •    i  •        Tenney's  Zoology. 

their  large  size  and  quickness  in 

diving.     They  are  migratory,  laying  two  or  three  eggs  in 

rushes  near  the  water's  edge. 

The  petrels,  gulls,  and  terns  (Fig.  463,  roseate  tern)  rep- 


542 


ZOOLOGY. 


resent  the  group  of  long-winged  swimmers  (Longipennes). 
They  have  long,  slender,  compressed  bills,  long,  sharp  wings, 
immense  powers  of  flight,  and  lay  their  eggs  in  rude  nests 
on  rocks  or  upon  the  ground.  The  most  notable  member 
of  the  group  is  the  albatross  (Diomedea  exulans)  of  the  South- 
ern hemisphere.  Its  wings  expand  more  than  three  metres 
(nearly  ten  feet).  It  lays  a  single  egg  12  cm.  long,  and 
spends  most  of  its  life  on  the  ocean  far  away  from  land. 
The  sooty  albatross  (D.  fuliginosa  Lawrence,  Fig.  464),  is 
occasionally  seen  on  our  coast. 


Fig.  4&4.— Sooty  Albatross.— From  Cones'  Key. 

These  birds  are  succeeded  in  the  ascending  series  by  the 
tropic-bird,  frigate  or  man-of-war  bird,  the  darter  or  snake- 
bird,  the  cormorants,  pelicans,  and  gannets  (Steganopodes), 
in  which  all  four  toes  are  fully  webbed,  the  web  reaching  to 
the  tips  of  the  toes.  The  body,  especially  in  the  pelicans  and 
gannets,  is  buo3^ed  up  more  than  in  other  birds  by  a  large 
number  of  much  subdivided  air-cells  under  the  subcutane- 
ous areolar  tissue  of  the  body. 

The  pelican  is  remarkable  for  the  large,  loose  pouch  on 
the  under  jaw,  capable  of  holding  several  quarts,  or  several 


SWIMMING  BIRDS. 


o43 


hundred  small  fishes.  In  the  East  Indies,  pelicans  are 
tamed  and  used  by  the  natives  in  fishing,  as  is  the  cormorant 
in  China,  while  in  early  times  it  was  in  England. 

The  ducks  and  geese  (Lamellirostres)  have  usually  broad 
bills  furnished  with  lamellate,  teeth-like  projections.  The 
feet  are  palmated,  adapted  for  swimming  rapidly.  In  the 
mergansers  the  bill  is  narrow  and  more  strongly  toothed. 
The  eider  duck  (Somateria  mollissima)  breeds  from  Labra- 
dor around  northward  to  Scotland,  plucks  its  down  from  its 
breast,  building  with  it  a  large  loose  warm  nest  under  low 
bushes  on  the  sea-coast,  where  it  lays  three  or  four  pale 


Fig.  465.— Summer  Duck.— From  Cones'  Key. 

dull  green  eggs.  The  canvas-back  (Fuligula  vaUisneria) 
feeds,  as  its  specific  name  implies,  on  the  wild  celery  ( Val- 
lisneria)  on  the  middle  Atlantic  coast  in  winter,  whence  it 
derives  its  delicious  flavor.  The  summer  duck  (Aixsponsa, 
Fig.  465)  breeds  in  trees.  The  original  source  of  our  do- 
mestic duck  is  the  mallard,  or  Anas  boschas.  It  is  known 
to  cross  with  various  other  species.  Upward  of  fifty  kinds 
of  hybrid  ducks  are  recorded,  some  of  which  have  proved 
to  be  fertile  (Coues).  The  black  duck  (Anas  obscura)  is 
abundant  on  the  shores  of  Northeastern  America,  and  is  fre- 


544 


ZOOLOGY. 


quently  brought  into  the  market.     The  wild  goose  (Branta 

Canadensis)  breeds  in  the  North- 
ern United  States  and  in  British 
America.  While  it  usually  breeds 
on  the  shores  of  rivers,  it  has 
been  known  in  Colorado  and 
Montana  to  nest  in  trees.  Allied 
to  it  is  the  barnacle  goose  of 
Europe  (Branta  leucopsis), which 
very  rarely  occurs  in  this  coun- 
Fig.  466. -Carolina  Kail. -From  try.  The  swans  are  characterized 

C/OU6S    Jv6y.  _  1 1       • 

by  their  long  necks,  the  trachea 

or  wind-pipe  being  remarkably  long,  especially  in  the  trum- 
peter swan,  where  it  enters  a  cavity  in  the  breast-bone, 
makes  a  turn  and   enters  the   lungs, 
after  forming  a  large  coil. 

To  this  group,  or  next  to  it,  also 
belong  the  flamingoes,  the  American 
flamingo  (Phcenicopterus  ruler)  occur- 
ring on  the  Florida  and  G-ulf  coast. 
Its  feathers  are  scarlet,  its  bill  yellow, 
large  and  thick,  while  the  legs  and 
neck  are  of  great  length.  It  connects 
the  swimming  with  the  wading  birds. 
The  foregoing  group  forms  a  division 
called  the  Natatores  or  swimming 
birds.  We  now  come  to  the  Gralla- 
tores  or  wading  birds,  which  have  long, 
naked  legs,  and  therefore  long  necks, 
with  usually  remarkably  long  bills. 
They  are  divided  into  cranes,  rails,  etc. 
(Alectorides),  the  herons  and  their 
allies  (Herodiones),  and  the  shore-birds, 
snipes  and  plovers,  or  Limicolce. 

The  cranes,  together  with  rails  (Por- 
sana  Carolina,    Fig.    466)   sometimes 
have  lobate  feet,  the  toes  are  often  JSXfS^iSmf 
long,  and  in  some  forms,  such  as  the 
coots  and  gallinules,  there  is  an  approach  to  the  ducks. 


UNIVERSITY 

Of 


WADING 


545 


Fig.  468.— Long-billed  Curlew.— From 
Cones'  Key. 


Allied  to  the  gallinules  is  the  "  giant  "  Or  Gallinula  (Le- 
guatia)  gigantea  of  Schlegel  (Fig.  467),  which  formerly  lived 
in  the  Mascarene  Islands,  having  been  observed  as  late  as 
]  694.  It  stood  two  metres  (over  six  feet)  high.  With  it  was 

associated  a  large  blue  galli- 
nule  —  Porphyrio  (Notornis  f) 
cwrulescens  Selys  —  which  was 
last  seen  on  the  Isle  Bourbon 
between  1669  and  1672.  It 
was  incapable  of  flight,  but 
ran  with  exceeding  swiftness. 
The  cranes  are  of  great 
stature,  the  legs  and  neck  very 
long,  with  the  head  sometimes 
curiously  tufted.  With  the 
true  herons  are  associated  the  night  herons  and  the  bitterns 
of  the  United  States,  the  boat-billed  heron  of  Central  Am- 
erica, and  the  odd  Balceniceps  rex  of  Africa,  which  has  an 
enormous  head  and  broad,  large  bill.  The  herons  are  suc- 
ceeded by  the  singular  spoon-bills  represented  by  the  rose- 
ate spoon-bill,  and  which,  with 
the  wood  Ibis  and  other  species 
of  this  group,  adorn  the  swamps 
and  bayous  of  the  South  Atlan- 
tic and  Gulf  States. 

The  shore-birds,  or  the  cur- 
lews (Numenius  longirostris, 
Fig.  468),  plover,  sandpipes, 
peeps,  snipes  (Gallinago  Wil- 
sonii,  Fig.  469),  woodcock,  and 
stilt  (Himantopus  nigricollis, 
Fig.  470),  are  long-legged,  long- 
billed  birds,  going  in  flocks  by 
the  seashore  or  river-banks, 
sometimes  living  inland  on  low 
plains  ;  they  are  not,  generally  speaking,  nest-builders,  the 
eggs  being  laid  in  rude  nests  or  hollows  in  the  ground. 
They  feed  on  worms,  insects,  and  snails,  either  picking 
them  up  from  the  surface  or  boring  for  them  in  the  mud  or 


Fig.  469.— American 
Cones'  Key. 


Snipe.— From 


546 


ZOOL00T. 


Fig.  470.— Stilt.— Prom  Cones'  Key. 


sand,  or  forcing  the  vermian  food  out  of  their  holes  by 

stamping  on  the  ground. 

Connecting  in  some  degree 
the  waders  and  gallinaceous 
fowl  are  the  bustards  of  the 
Old  World,  certain  strange 
exotic  birds,  especially  the 
horned  screamers  represented 
by  a  very  rare 'bird,  the  Pala- 
medea  cornuta  Linn.,  which 
has  sharp  horns  on  the  wings. 
The  form  of  the  gallina- 
ceous birds,  formerly  called 
Rasores,  from  their  peculiar 
habit  of  scratching  the  ground 
for  food,  is  readily  recalled 
by  a  simple  enumeration  of 
the  partridge,  Oreortyx  (0. 

pictus,  Fig.  471),  quail  (Ortyx),  ptarmigan  (Lagopus,  Fig. 

472),  pinnated  grouse  or  prairie  hen  (Cupidonia  cupido], 

sage-cock,  Canada  grouse 

or  spruce  partridge   (Te- 

trao),    and    wild    turkey 

(Meleagris),  as  well  as  the 

exotic  forms,  the  pheasant 

of  the  Old  World,  the  use- 
ful hen  or  barn-yard  fowl, 

which  is  a  descendant  of 

Gallus     Bankiva      Tem- 

minck,  of  India.  These  are 

allied  to  the  argus-pheasant 

and  the  peacock,  the  latter 

rivalling  the  humming- 
birds in  its  gorgeous  plum- 
age. The  guinea-hen  is 

an  African  bird.     To  this 

group  belongs  the  CUrioUS    Ke*^  m- ~Plumed  Partridge.-From  Cones' 

mound-bird  (Megapodius), 

of  Australia  and  New  Guinea.     It  heaps  up  a  large  mass  of 


GALLINACEOUS  BIRDS. 


547 


rubbish,  forming  a  hot-bed,  in  which  its  eggs  are  left  to 
hatch.  The  megapods,  together  with  the  American  guans 
and  curassows  (Cracidce),  form  a  sort  of  passage  from  the 
gallinaceous  to  the  columbine  birds.  One  of  the  most  puz- 
zling forms  for  the  systematic  ornithologist  to  deal  with  is 
the  hoasin  of  Guiana  ( Opisthocomus  cristatus  Illiger).  In 
this  bird  the  keel  of  the  breast-bone  is 
cut  away  in  front,  the  wish-bone  unites 
with  the  coracoid  bones,  and  also  with 
the  manubrium  of  the  breast-bone,  a 
thing  of  rare  occurrence  (Coues). 

In  the  tinamous  of  Central  and  South 
America  the  tail-feathers  are,  in  some 
cases,  entirely  wanting,  and  the  breast- 
bone and  skull-bones  have  some  anom- 
alous features.     Most  all  gallinaceous 
birds   have   plump 
bodies,  with  short 
beaks    and     small 
rounded  wings,  not 
being    good   fliers. 
In    some   of    their 
cranial     characters  ^ 
they  are  so  peculiar 
that  Huxley  makes 
them    one    of    his 
primary     divisions 
of  Carinatce. 

We  now  come  to 
birds  of    a  higher 

1  •   i     j/i  FlS-  472-— White-tailed  Ptarmigan  (Lagopvs  leucurus\ 

type,  in  WniCn  the  in  (upper  figure)  summer  and  Qower  figure)  winter 
knee  and  part  of  P1*^--^  ****»'•  Survey. 

the  thigh  are  free  from  the  body,  the  leg  being  usually 
feathered  down  to  the  tibio-tarsal  joint ;  the  toes  are  usually 
on  the  same  level,  being  fitted  for  grasping  or  perching. 

The  doves  are  .rapid  fliers,  but  a  notable  exception  is  seen 
in  their  extinct  ally  the  Dodo  (Didus  ineptus  Linn.)  of 
Mauritius,  which  became  extinct  on  the  island  of  Mauritius 
iu  the  seventeenth  century,  while  the  solitaire,  Didus  (Pe- 


548  ZOOLOGY. 

zopliaps)  solitarius  Schlegel,  inhabited  the  island  of  Ro- 
driguez, having  been  exterminated  about  the  same  date 
(1681).  These  were  clumsy,  defenceless  birds,  incapable  of 
flight,  and  were  destroyed  by  the  domestic  animals  which 
accompanied  the  Portuguese  voyagers  to  the  Mascarene 
Islands.  The  doves  and  their  allies  now  commonly  form  a 
group,  called  Columbcs. 

The  birds  of  prey  (Raptor es],  comprising  the  vultures, 
buzzards,  falcons,  hawks,  eagles,  and  nocturnal  owls,  have 
a  hooked  and  cered  beak — i.e.,  with  a  waxy,  dense  mem- 
brane situated  at  the  base  of  the  upper  mandible.  The 
claws  are  large  and  sharp.  The  raptorial  birds  live  either  on 
birds  and  mammals,  or  fish,  reptiles,  batrachians,  and  insects. 
Of  the  vultures,  the  most  notable  for  size  is  the  condor  of 
the  Andes  (Sarcorhampusgryphus),  which  has  great  powers 
of  flight,  its  wings  expanding  nearly  three  metres  (nine 
feet). 

The  carrion  crow  and  turkey  buzzard  ( CatJiartes  atratus 
and  (7.  aura  Illig.)  are  useful  as  scavengers,  especially  the 
former,  which  is  partly  domesticated  in  southern  cities  and 
towns  ;  they  nest  on  the  ground  or  in  stumps,  and  are  more 
or  less  social.  The  bald-headed  eagle  (Haliaetus  leucocepha- 
his)  is  dark-brown  when  young,  and  before  shedding  its 
youthful  plumage  is  larger  than  the  white-headed  adult.  It 
nests  on  inaccessible  rocky  points  ;  is  the  sworn  enemy  of 
the  fish-hawk,  and,  like  it,  fond  of  fish,  often  wresting  its 
living  food  from  the  talons  of  the  hawk.  This  species  is  the 
emblem  of  our  country.  The  osprey  or  fish-hawk  (Pandion 
haliaetus)  is  two-thirds  of  a  metre  long,  nests  in  tall  trees, 
and  is  migratory.  Among  the  hawks,  the  most  notable  are 
the  falcons  or  hunting  hawks,  used  during  the  Middle  Ages 
in  hunting  the  hare,  etc. ;  in  nature  they  chase  their  prey 
and  kill  it  immediately,  devouring  it,  and  rejecting  the 
bones  and  hair  of  the  partly  digested  food  in  a  ball  from  the 
mouth. 

The  owl  is  a  bird  of  the  night ;  its  flight  is  noiseless,  ow- 
ing to  its  soft  plumage,  the  feathers  having  no  after-shaft. 
It  has  large  eyes  and  a  hooked  bill,  giving  the  bird  of  Mi- 
nerva an  air  of  consummate  wisdom,  Owls  capture  living 


BIRDS  OF  PREY.  549 

mice  and  other  small  nocturnal  animals,  ejecting  from  the 
mouth  a  ball  of  the  indigestible  portions  of  their  meal. 
The  little  burrowing  owl  of  the  western  plains  (Spheotyto 
cunicularia,  var.  hypogcea)  consorts  with  the  prairie  dogs  and 
rattlesnakes,  nesting  in  the  holes  when  deserted.  Their 
rusty,  dull  hues  assimilate  them  with  the  color  of  the  soil 
they  inhabit.  Our  largest  owl  is  the  great  gray  owl  (Syr- 
nium  cinereum) ;  it  is  nearly  f  metre  (2|  feet)  in  length,  and 


Fig.  473.— Carolina  Parroquet.— From  Coues'  Key. 


is  an  inhabitant  of  Arctic  America.  A  visitor  in  winter 
from  the  Arctic  regions  is  the  snowy  owl  (Nyctea  nivea), 
which  is  nearlyf  m.,  or  two  feet  long.  The  great  horaed 
owl  (Bubo  Virginianus)  is  about  the  same  size  as  the  snowy 
owl,  but  has  two  conspicuous  ear-tufts,  adding  to  its  height 
and  its  general  impressiveness  as  a  bird  of  more  than  ordi- 
nary sagacity. 

Of  more  intelligence  and  gifted  with  the  power  of  speech 


550 


ZOOLOGY. 


are  the  parrots  (Psittaci).  The  tongue  is  large,  soft,  and 
remarkably  mobile,  as  the  muscles  at  the  base  are  more  dis- 
tinctly developed  than  in  other  birds,  and  the  lower  larynx 
is  complicated  with  three  pairs  of  muscles  ;  hence  these 
birds  are  wonderful  mimickers  of  the  human  voice,  imi- 
tating the  laughter  or  crying  of  babies,  and  repeating  brief 
sentences,  while  some  sing.  In  proportion  to  their  capacity 
for  talking,  parrots  command  a  very 
high  market  price.  Their  toes  are  in 
pairs,  the  bill  is  cered  and  very  stout, 
adapted  for  cracking  hard  nuts.  The 
wish-bone  is  sometimes  rudimentary, 
and  the  sternum  entire,  not  notched. 
Parrots  are  monogamous,  like  the  hawks, 
and  nest  in  rocks  or  hollow  trees.  Our 
only  parrot  is  the  Carolina  parroquet 
(Conurus  Carolinensis  Kuhl,  Fig.  473), 
which  is  common  in  Florida.  It  for- 
merly extended  to  the  Great  Lakes  and 
to  New  York,  but  is  nearly  exterminated. 
About  three  hundred  and  fifty  species 
are  scattered  through  tropical  countries, 
Australia  and  South  America  being 
especially  favored  by  these  gorgeous 
birds.  The  ground  parrot  of  New  Zea- 
land does  not  fly,  all  the  others  being 

Fig.  474.—  Skull  of  Ge-   good  fliei'S. 
cinus  viridis  L.,  showing 

the  asymmetrical  position 


Ohp3g 


.,,,          •»-»•.  t     i          •        -n 

The  Picaricv,  a  somewhat  miscella- 
neous  group  of  birds,  comprising  the 
woodpeckers,  the  cuckoos,  and  allies, 
and  the  swifts  and  humming-birds,  con- 
nect the  preceding  groups  with  the  Pas- 
serine or  singing  birds.  From  the  latter  the  Picarice  com- 
monly differ  in  the  form  of  the  sternum,  in  the  less 
developed  vocal  apparatus,  there  being  no  more  than  three 
pairs  of  separate  muscles,  so  that  the  birds  are  not  musical  ; 
as  well  as  in  the  nature  of  the  toes  and  wing  and  tail 
feathers. 

The  woodpeckers  usually  have  pointed,  stiff  tail-feathers, 


PERCHING  BIRDS. 


551 


and  the  bill  is  straight  and  strong.  The  tongue  is  long, 
flat,  horny,  and  barbed  at  the  end,  and  can  be  usually  darted 
out  with  great  force,  so  that  the  bird  can  make  holes  in  the 
bark  of  trees  and  draw  out  the  larvae  of  insects  boring  under 
the  bark  ;  in  this  way  these  birds  render  us  signal  service. 
The  tongue,  as  in  all  vertebrates,  is  supported  by  the  hyoid 
apparatus,  especially  by  two  cartilaginous  appendages  to  the 
hyoid  bone,  called  "  the  horns. "  These  in  the  woodpeckers, 
when  fully  developed,  are  curved  into  wide  arches,  each 
horn  making  a  loop  down  the  neck,  and  thence  bending 
upward,  sliding  around  the 
skull,  and  even  down  on  the 
forehead.  Through  a  peculiar 
muscular  arrangement  of  the 
sheaths  in  which  the  horns  slide, 
they  can  be  retracted  down  on 
the  occiput,  and  work  as  springs 
on  the  base  of  the  tongue,  forc- 
ing it  out  with  great  velocity. 
Lindahl  has  noticed  in  some 
European  woodpeckers  an  asym- 
metric arrangement  of  the  horns 
as  indicated  in  Fig.  474. 

The  second  group,  the  Cuculi. 
comprise  the  hoopoes,  horn-bills, 
kingfishers,  toucans,  and  cuck- 
oos. These  are  succeeded  by 
the  Cypseli,  embracing  the  hum- 
ming-birds, goatsuckers,  swifts, 
nighthawk  (Ohordeiles  Virginianus,  Fig.  475),  and  whip- 
poorwill,  which  have  long  pointed  wings,  great  powers 
of  flight,  small  weak  feet,  and,  in  the  humming-birds, 
long  slender  bills.  The  latter  are  peculiar  to  America, 
being  chiefly  confined  to  South  and  Central  America,  only 
one  species  (Trochilus  colubris  Linn.)  extending  into  the 
Eastern  United  States,  though  a  dozen  or  more  species  oc- 
cur in  the  Western  United  States,  and  very  many  in  Mexico. 
,  The  highest  group  of  birds,  those  which  sing,  are  the 
Passeres  or  perchers.  In  these  birds  the  feet  are  adapted  for 


Pig.      475.  —  Nighthawk. 
Coues'  Key. 


From 


552 


ZOOLOGY. 


grasping,  one  toe  projecting  backward,  while  the  bill  is  horny, 
usually  sharp — conical,  according  to  Coues.  Various  as  are 
the  shape  of  the  wings,  they  agree  in  having  the  great  row 
of  coverts  not  longer  than  half  the  secondaries  ;  the  pri- 
maries either  nine  or  ten  in  number,  and  the  secondaries 
more  than  six.  The  tail,  extremely  variable  in  shape,  has 
twelve  rectrices  (with  certain  anomalous  exceptions).  There 
is  but  one  common  carotid  artery,  and  the  sternum  is  very 
uniform  in  shape.  Their  high  physical  irritability  is  co- 
ordinate with  the  rapidity  of  their  respiration  and  circula- 
tion ;  they  consume  the  most  oxygen  and  live  the  fastest 
of  all  birds  (Coues). 

There  are  two  groups  of 
Passerine  birds,  differing  in 
the  structure  of  the  lower 
larynx ;  in  the  first  ( Clama- 
tores)  the  vocal  organs  are 
more  or  less  rudimentary, 
the  species  not  being  singers, 
while  in  the  second  and 
higher  division  (Oscines)  the 
lower  larynx  is  so  developed 
that  most  of  the  species  ex- 
cel as  singers.  In  the  sing- 
ing birds  the  vocal  apparatus 
(syrinx),  or  lower  larynx,  is 
situated  next  to  the  lungs  at 
the  end  of  the  windpipe,  with  a  muscular  apparatus  formed 
of  five  or  six  pairs  of  muscles,  whose  action  varies  the 
tension  of  the  vocal  cords  and  narrows  or  widens  the 
glottides,  which  are  elastic  folds  of  the  mucous  membrane. 
A  fold  of  the  tympanal  membrane  of  the  syrinx,  called  the 
memlrana  semilunaris,  projects  inward. 

Representatives  of  the  Clamatores  are  the  Acadian  fly- 
catcher, the  wood  pewee,  the  pewee  or  phcabe-bird,  and  the 
kingbird  (Fig.  476).  The  last,  sometimes  called  the  bee- 
martin,  Coues  tells  us,  destroys  a  thousand  noxious  insects 
for  every  bee  it  eats.  The  lyre-bird  (Fig.  477)  is  also  a 
member  of  this  group. 


Fig.  476.-Kingbird.— From  Coues'  Key. 


SINGING  BIRDS. 


553 


This  bird,  with  tail  feathers  so  strikingly  developed  (Fig. 
477),  is  so  peculiar  among  higher  Passeres  that  it  has  been 
proposed  to  separate  it,  with  certain  probable  allies,  from 
all  the  rest. 

The  Oscines  are  represented  by  a  host  of  species.  These 
birds  stand  at  the  head  of  their  class  ;  and  as  they  are  mostly 


Pig.  477.— The  Lyre-bird  of  Australia  ( Menura  superba). 

of  small  size,  it  may  be  said  of  them  that  they  excel  in  qual- 
ity, not  quantity  ;  most  of  them  sing,  being  highly  wrought, 
exquisite  winged  gems.  Among  the  most  notable  are  the 
jays,  including  the  magpie  of  the  Rocky  Mountains  (Fig. 


554  ZOOLOGY. 


478),  the  crow,  and  blackbird,  so  useful  a  bird,  notwith- 
standing its  mischievous  propensities ;   the  oriole,    whose 


Fig.  478.— Magpie.— Prom  Cones'  Key. 


Fig.  479.— Butcher-bird.— From  Cones'  Key. 

hanging  nest,  brilliant  colors,  and  lively  song  render  it  one 
of  our  most  interesting  birds  ;   while  the  reed-bird  of  the 


SINGING  BIRDS. 


555 


Fig.  480.— Warbling  Vireo.— From 
Coues'  Key. 


South  or  bobolink,  as  it  is  called  in  the  North,  wakes  up  the 
meadows  with  his  lively  notes.  The  finches  with  their 
conical  beaks  are  succeeded,  in  the  ascending  series,  by  the 
English  sparrow,  a  bird  useful  in  the  cities  in  destroying 

canker-worms,  but  a  nuisance  in 
the  country.  Our  song-sparrow 
(Melospiza  fasciata)  is  widely 
distributed,  and  everywhere 
commends  itself  by  its  pleasant 
notes.  Quite  opposed  in  its 
habits  is  the  butcher-bird  or 
shrike  (Fig.  479),  a  quarrelsome, 
rapacious  bird,  which  feeds  on 
insects  or  small  mammals,  often 
impaling  them  on  thorns  or  sharp 
twigs,  and  leaving  them  there.  The  group  of  vireos  or 
greenlets  (Fig.  480)  are  peculiar  to  America  ;  their  bills  are 
hooked,  with  a  notch  at  base  ;  they  are  warblers.  The  wax- 
wing  (Ampelis  cedrorum,  Fig.  481)  is  the  type  of  an  allied 
family.  The  swallows  and 
martins  are  interesting  from 
the  change  made  in  the  nest- 
ing habits  of  the  more  com- 
mon species  which  rear  their 
young  in  artificial  nests  or 
in  barns,  or  under  the  eaves 
of  buildings. 

Another  group  character- 
istic of  North  America  is 
the  warblers,  Dendrceca  (D. 
virens,  Fig.  482)  being  the 
representative  genus.  On 
the  other  hand,  the  larks 
are  an  Old  World  assemblage 
of  birds,  but  few  species 
occurring  in  this  country,  while  the  wrens  (Fig.  483)  are 
mostly  restricted  to  America. 

The  smallest  bird  in  the  United  States,  except  the  hum- 
ming-bird,   is  the  gold-crested  kinglet    (Regulus    satrapa 


Fig.    481  .—Carolina 
Coues'  Key. 


Wax  win  54  —  From 


556  ZOOLOGY. 

Lichtenstein),  which  is  less  than  9  cm.  (3f  inches)  in  length. 
Lastly  come  the  bluebird,  the  melodious  thrushes,  and  the 


Kg.  482.— Black-throated  Green  Warbler.— From  Coues'  Key. 


Fig.  483.— Winter  Wren.— From  Coues'  Key. 

mocking-bird,  while  at  the  head  of  the  class  in  this  country 
stands  the  robin  (Turdus  migratorius  Linn.). 


CLASSIFICATION  OF  BIRDS.  56? 


CLASS  VI.— AVES. 

Feathered  Vertebrates;  jaws  encased  in  horny  beaks  in  existing  forms  ; 
the  fore-limbs  forming  wings  ;  warm-blooded  ;  heart  four-chambered  ; 
lungs  with  accessory  air-sacs  ;  the  bones  dense,  hollow  ;  oviparous  ;  eggs 
very  large,  covered  by  a  calcareous  shell. 

Sub-class  1.  Saururce. — Tail  as  long  as  the  body  ;  head  and  fore  limbs 
reptilian  ;  with  feathers,  scales,  and  teeth.  (Archaeopteryx.*) 

Sub-class  2.  Odontornithes. — Vertebrae  biconcave,  or  as  usual ;  jaws 
slender,  with  teeth  implanted  in  sockets  or  in  grooves;  meta- 
carpals  co-ossified  ;  sternum  keeled  or  unkeeled  ;  wings  well 
developed.  (Ichthyornis.) 

Sub-class  3.  Ratitce. — Sternum  smooth  ;  wings  rudimentary.   (Struthio). 

Sub-class  4.  Carinatce. — Sternum  keeled  ;  wings  well  developed.  (Tur- 
dus. 

Laboratory  Work. — The  student  should  prepare  a  skeleton  of  a  hen  or 
any  other  bird,  and  compare  it,  and  especially  the  skull  and  limbs,  with 
those  of  a  reptile  and  a  mammal.  In  dissecting  a  pigeon  or  fowl,  at- 
tention should  be  given  to  those  points  previously  indicated  in  which 
birds  diverge  from  reptiles  on  the  one  hand  and  mammals  on  the  other. 


CLASS  VII.  —  MAMMALIA  (Mammals). 

General  Characters  of  Mammals.— In  the  mammals,  which 
begin  with  the  duck-bill,  a  creature  in  some  respects  re- 
minding us  of  the  birds,  and  end  with  man,  we  observe, 
as  compared  with  birds,  an  increased  complexity  of  struc- 
ture ;  and  in  the  nature  of  the  work  done  by  the  different 
organs,  we  may  see  a  constant  tendency  to  a  development 
of  parts  headward,  so  that  the  head  becomes  large  in  pro- 
portion to  the  body,  the  brain  increases  in  size,  and  the  fore- 
limbs  finally  become  hands,  ministering  to  the  intellectual 
wants  of  the  animal.  Also,  as  we  ascend  the  series,  the  body, 
from  being  horizontal,  with  limbs  adapted  for  walking  on  all 
fours,  becomes  finally  in  the  apes  semi-erect,  in  man  wholly  so. 

The  greatest  step  in  advance  over  the  reptiles  and  birds 

*  Vogt  believes  that  this  is  a  bird -like  reptile  ;  a  more  perfectly  pre- 
served specimen  having  lately  been  found,  showing  that  the  head  and 
fore  part  of  the  body  were  more  reptilian  than  Owen  supposed. 


558  ZOOLOGY. 

is  in  the  nature  of  the  limbs,  the  structure  of  the  head,  the 
organs  of  special  sense,  together  with  the  increased  com- 
plexity of  the  teeth,  and  the  size  and  complicated  structure 
of  the  brain,  particularly  of  the  cerebrum  and  cerebellum. 

The  more  important  (diagnostic)  features  of  the  mammals 
are  the  articulation  of  the  lower  jaw  directly  to  the  skull, 
the  quadrate  bone  becoming  one  of  the  ear-bones  (the  mal- 
leus) ;  there  are  two  occipital  condyles  ;  the  teeth  are  differ- 
entiated into  incisors,  canines,  premolars,  and  molars  ;  the 
body  is  covered  with  hair.  The  body-cavity  is  divided  into 
two  compartments  (thorax  and  abdomen)  by  a  large  muscle, 
the  diaphragm,  so  that  the  lungs  are  separated  from  the  ab- 
dominal viscera.  From  the  four-chambered  heart  the 
single  aorta  is  reflected  over  the  left  bronchus  ;  the  blood  is 
warm, with  non-nucleated  corpuscles  ;  the  circulation  is  com- 
plete, the  blood  being  entirely  received  by  the  right  auricle 
and  transmitted  by  the  right  ventricle  to  the  lungs  for  aera- 
tion, whence  it  is  after  ,vard  returned  by  the  left  ventricle 
through  the  system.  The  brain  is  much  larger  than  in 
birds,  the  cerebral  hemispheres  forming  the  bulk  of  the 
brain,  and  gradually,  in  different  members  of  the  ascending 
series,  overarching  and  finally  concealing  from  above  the 
cerebellum.  The  cerebral  hemispheres  are  more  or  less 
connected  (and  in  nearly  inverse  ratio)  by  an  anterior  com- 
missure and  a  superior  transverse  commissure  (corpus  callo- 
8um\  the  latter  more  or  less  roofing  in  the  lateral  ventricles 
(Gill):  Mammals  are  viviparous,  the  embryo  developing 
from  a  minute  egg,  and  the  young  after  birth  are  fed  by 
the  mother  with  milk  secreted  in  the  mammae  or  mammary 
glands  ;  hence  the  name  of  the  class,  Mammalia. 

Returning  to  the  skeleton,  which  we  may  examine  more 
in  detail  :  the  skull,  as  a  brain-box,  is  much  larger  than  in 
the  reptiles  and  birds.  The  brain-cavity  of  Coryplwdon 
and  other  extinct  Tertiary  mammals  was  exceedingly  small, 
scarcely  larger  in  proportion  than  in  reptiles,  and  there  is  a 
progressive  increase  in  size  of  the  cavity  of  the  skull  in  the 
more  specialized  descendants  of  this  early  Tertiary  type,  as 
seen  in  that  of  the  horse,  when  compared  with  its  Eocene 
progenitors.  There  is  also  a  decided  increase  in  the  bruin- 


STRUCTURE  OF  MAMMALS.  559 

box  of  the  monkey  as  compared  with  that  of  the  lemur,  and 
of  apes  as  compared  with  monkeys,  while  in  man  the  brain 
capacity  is  twice  that  of  the  highest  apes. 

The  different  regions  of  the  vertebral  column  are  better 
defined  than  in  the  birds  and  reptiles  ;  this  is  seen  in  the 
cervical  vertebrae,  the  number  of  which  is  usually  seven. 
The  exceptions  to  this  rule  are  few,  there  being  six  in  one 
sloth  (Cholwpus),  eight  or  nine  in  another  sloth  (Bradypus), 
and  six  in  the  American  manatee.  Behind  the  cervical  is 
the  dorsal  region,  consisting  of  from  ten  to  twenty-four, 
usually  thirteen,  vertebrae,  and  the  lumbar  region,  which  is 
composed  of  from  two  to  nine,  usually  six  or  seven,  vertebrae, 
and  is  marked  off  by  the  absence  of  movable  ribs.  The 


Pig.  484.— Skull  of  the  Lion.— After  Owen. 

shoulder-girdle  is  not  solidly  united  to  the  dorsal  vertebrae, 
but  loosely  attached  by  muscles  and  tendons.  The  pelvis 
—i.e.,  that  portion  called  the  ilium — connects  with  a  single, 
sometimes  two,  rarely  three,  vertebrae  of  the  sacral  region, 
and  the  union  of  these  vertebrae  with  one  or  more  caudal 
vertebrae  forms  an  assemblage  of  consolidated  vertebrae,  called 
the  os  sacrum,  which  in  the  sloths,  or  Edentates,  comprises 
eight  or  nine  vertebrae.  The  number  of  caudal  vertebras 
in  the  monkeys  may  amount  to  thirty,  in  the  long-tailed 
manis  (Fig.  501)  to  forty,  while  in  other  mammals  there  may 
be  less  than  this  number,  there  being  four  retained  by  man 
and  the  larger  apes,  while  in  some  bats  there  are  only 
three. 


560 


ZOOLOGY. 


But  it  is  in  the  limbs,  and  especially  the  feet,  of  mammals 
that  the  skeleton  varies  most,  and  always  in  accordance  with 
the  different  habits  of  the  creature.  The  limbs  of  mammals 
differ  from  those  of  the  lower  vertebrates  in  the  fact  stated 
by  Gegenbaur,  that  the  planes  in  which  the  angles  of  the 
limbs  of  either  side  are  set  are  parallel  to  the  vertical  me- 
dian plane  of  the  body,  thus  giving  greater  independence  to 
the  limbs,  which  now  become  supports  for  the  body,  since 
they  raise  it  from  the  ground.  Beside  this,  the  angles  be- 
tween the  equivalent  portions  in  each  limb  do  not  agree 

with  each  other,  as  in  the  rep- 
tiles, but  point  in  an  opposite 
direction  in  the  case  of  the  fore 
and  hind  limbs  respectively 
(Gegenbaur).  As  we  ascend  in 
the  mammalian  series,  the  limbs, 
particularly  the  fore-limbs,  are 
variously  modified.  The  limbs 
of  whales  are  paddle-like,  though 
the  bones  of  the  limbs  are  homo- 
logous with  those  of  other  mam- 
mals. The  feet  of  the  seal  are 
webbed,  forming  nippers  ;  it  can- 
not support  itself  on  its  limbs, 
but  the  fore-feet  have  consider- 
able motion  of  the  radius  on  the 
ulna.  In  the  dog  the  fore-limbs 
have  but  little  motion  of  the 
radius  on  the  ulna,  but  the  cats 
(Felidce)  have  more  of  this  rotary 
motion,  enabling  them  to  grasp  with  the  fore-foot.  This 
rotary  motion  of  the  fore-arm,  involving  the  modification 
of  the  fore-foot  into  a  hand,  is  seen  in  the  thumbless  mon- 
keys (Fig.  485),  and  in  those  provided  with  a  thumb,  in  the 
gorilla,  and  especially  in  man.  The  extreme  of  specializa- 
tion of  all  four  limbs  is  seen  in  the  horse,  which  has  but 
one  digit,  and  walks  on  its  single  toe-nail.  In  the  bat,  the 
ulna  and  radius  are  fused  together  as  one  bone,  and  the 
last  three  fingers  are  greatly  lengthened.  The  liberation  of 


Fig.  485.— Arm  of  the  Thumbless 
Monkey  (Ateles). 


HAIR  AND  HORNS  OF  MAMMALS. 


561 


the  limb  from  the  body  becomes  more  marked  as  we  ap- 
proach man.  In  the  seal,  only  the  wrist  protrudes  from 
the  skin,  the  limb  of  the  otter  slightly  more ;  the  horse's 
leg  does  not  protrude  beyond  the  elbow,  that  of  the  monkey 
projects  two  thirds  of  its  length,  while  in  man  the  limbs 
become  wholly  free  from  the  trunk  (Wyman). 

The  hairs  origin  ate  in  minute  sacs  which  extend  from  the 
epidermis  into  the  cutis  ;  from  the  bottom  of  this  inpushing 
of  the  epidermis  grows  up  the  shaft  of  the  hair,  which  is 


Fig.  486.— Diagram  of  the  development  of  the  nipple  ;  vertical  section,   (^periphery 
of  the  glandular  area  (b) ;  ffl,  glands.    A,  form  of  the  gland  in  Echidna ; 


in  most  mammals ; 
Gegenbaur. 


B,  its  form 
C\  'its"f6rm  in  some  ungulates,  &»  the  cow,  marej  etc.— After 


surrounded  at  the  base  by  the  cellular  wall  of  the  hair-sac 
forming  the  root-sheaths.  The  spines  of  the  porcupine,  the 
scales  of  the  Manis,  of  the  armadillo,  of  the  tail  of  the  rat, 
are  modified  hairs,  all  developing  in  the  same  manner. 

Many  mammals,  especially  the  ruminants,  as  the  deer,  ox, 
rhinoceros,  etc.,  are  armed  with  horns.  There  are  two 
kinds,  those  with  a  bony  core  surrounded  with  a  horny 
epidermal  case  as  in  the  deer ;  while  in  others,  as  the  ante- 
lopes, sheep,  goats,  and  oxen,  the  horns  are  hollow  ;  hence 


562 


ZOOLOGY. 


they  are  sometimes  called  Cavicorns.  In  most  horned 
mammals,  the  horns  are  persistent ;  in  the  deer  they  are 
dropped  annually  ;  in  the  prong-horned  antelope  (Fig.  487) 
the  horns  are  also  shed  annually. 

The  mammary  glands  are  modifications  of  the  tegument- 
ary  glands  which  are  found  in  all  vertebrates  except  fishes. 
In  the  duckbill  and  spiny  ant-eater  (Echidna),  these  glands 
retain  their  simple  elementary  nature.  In  all  others  nip- 
ples are  developed  (Fig.  486).  They  correspond  in  general 
to  the  number  of  young  in  a  litter. 

The  dentition  needs  careful  study  in  connection  with  the 


Fig.  488.— Skull  of  Ant-eater.— After  Owen. 


Pig.  487. -Hollow 
horn  of  the  Prong 
horned  Antelope. 


Fig.  489.— Skull  of  a  Porcupine.— After  Owen. 


fossil  remains  of  mammals,  as  the  different  orders  are  char- 
acterized in  great  part  by  the  differences  in  the  form  and 
number  of  the  teeth,  which  are  intimately  correlated  with 
the  structure  of  the  digestive  organs  and  the  nature  of  the 
limbs  ;  thus  while  vertebrae  are  useful  in  identifying  or  re- 
storing fossil  reptiles,  the  teeth  are  especially  serviceable  in 
classifying  fossil  mammals.  Some  existing  forms  are  en- 
tirely toothless,  as  the  duckbill,  where  the  teeth  are  repre- 
sented by  horny  plates,  and  the  ant-eater  (Fig.  488).  While 
the  sloths  have  no  incisors,  these  are  present  and  very 
large  in  the  rodents,  but  the  canines  are  absent  (Fig.  489), 


THE  EAR   OP  MAMMALS. 


563 


In  the  elephant  the  upper  canines  form  the  tusks,  the  cor- 
responding teeth  of  the  lower  jaw  being  absent.  In  many 
teeth,  as  those  of  the  deer  (Fig.  490),  the 
crown  of  the  molars  is  quite  convex,  with 
crescent-shaped  enamel  areas.  The  canines 
are  large  and  sabre-shaped  in  the  cat  fam- 
ily, while  in  the  pigs,  especially  the  baby- 
roussa  of  Malaysia,  the  upper  pair  curve 
upward  and  .backward  to  the  forehead. 
The  premolars  and  molars  have  two  or 
three  roots  or  fangs  ;  in  none  of  the  lower 
vertebrates  do  the  teeth  have  more  than 
one  root.  . 

The  organs  of  sense  are  much  developed,  especially  the 
ear.     The  quadrate  bone  of  the  reptiles  and  birds,  which  is 


Fig.  490.— Crown  of 
the  tooth  of  a  deer, 
showing  the  enamel 
crescents. —  After 
Owen. 


C-— 


Fig.  491.— Diagram  of  the  labyrinth  of  the  ear  in  7,  the  fish,  77,  the  h5rd,  and  777,  a 
mammal.  U,  utriculus;  S,  saccnlus;  US,  utriculus  and  eaccnlus;  C)\  canalis  reunieus  : 
R,  recessus  labyrinthi;  UC,  commencement  of  the  cochlea,  (7,  L,  lagena;  K,  ccecal 
sac  at  the  apex;  C,  coecal  sac  of  the  vestibulum  of  the  cochlear  canal.— After  Wai- 
deyer,  from  Gegenbaur. 

large,  external,  and  suspends  the  lower  jaw  to  the  skull,  now 
becomes  minute,  internal,  and  forms  one  of  the  internal 
bones  (malleus)  of  the  ear.  The  labyrinth  of  the  ear, 
largest  in  fishes,  is  smallest  in  mammals.  The  cochlea 


564  ZOOLOGY. 

(Fig.  491,  C)  is  greatly  developed  in  the  mammalia,  while 
the  external  ear  now  appears.  This  is  a  prolongation  of 
the  edges  of  the  first  branchial  cleft  of  the  embryo.  There 
is,  however,  no  external  ear  in  the  Monotrenies  (duckbill). 
It  is  also  absent  in  whales,  the  Sirenians  or  sea-cows,  in 
most  seals,  and  is  very  small  in  the  eared  seals  (Otaria). 
The  eye  of  mammals  is  not  essentially  different  from  that  of 
the  lower  vertebrates. 

The  general  anatomy  of  the  soft  parts  of  a  mammal  may 
be  studied  by  dissecting  a  cat,  with  the  aid  of  the  following 
description  and  drawings  prepared  by  Dr.  C.  S.  Minot : 

Fig.  492  illustrates  the  general  anatomy  of  the  cat ;  the 
skin  and  right  half  of  the  body- wall  have  been  removed. 
The  body-cavity  is  divided  into  an  anterior  and  posterior 
division  by  a  transverse  arched  partition,  the  diaphragm  (D), 
composed  of  a  thicker  peripheral  muscular  portion  and  a 
thinner  central  tendinous  part.  Through  the  latter  pass 
the  great  blood-vessels  and  the  oesophagus.  The  anterior 
chamber  is  the  thorax  or  pleural  cavity,  and  contains 
the  respiratory  organs  and  heart.  To  show  these,  the 
right  lung  has  been  removed.  The  heart  (Ht)  was  en- 
closed in  the  thin-walled  pericardial  sac,  which  has  been 
cut  away.  The  great  systemic  veins  enter  from  behind — 
i.e.)  dorsally ;  from  below  the  vena  cava  inferior,  passing 
up  through  the  diaphragm  and  uniting  opposite  the  heart 
with  the  large  vein,  cava  superior,  V,  from  above,  the  two 
emptying  into  the  right  auricle.  The  oesophagus  (Oe) 
overlies  the  trachea  (Tr).  The  aorta  arises  from  the  heart, 
and,  curving  upward  and  backward,  runs  to  the  left  of 
both  trachea  and  oesophagus,  as  indicated  by  the  dotted 
lines,  and  continues  its  backward  course  just  below  the  vena 
azygos,  into  the  abdomen.  The  trachea  gives  off  a  bronchus 
to  each  lung  (Lu).  The  lungs  are  sacculated  elastic  organs, 
with  no  main  central  cavity.  They  are  separated  dorsally  by 
a  thin  median  vertical  membrane  (M),  the  mediastinum,  the 
equivalent  of  the  mesentery  in  the  abdomen.  Lying  on  the 
side  of  the  vertebral  column  can  be  seen  part  of  one  of  the 
two  chains  of  sympathetic  nervous  ganglia  (S). 


ANATOMY  OF  THE  OAT. 

The  abdominal  cavity  contains  the  principal  reproduc- 
tive, excretory,  and  digestive  organs.  The  oesophagus  ter- 
minates in  the  stomach  almost  immediately  below  the  dia- 
phragm. The  stomach  (St)  occupies  a  transverse  position, 
its  larger  (cardiac)  end,  which  receives  the  oasophagus,  lying 
on  the  left,  the  smaller  (pyloric)  end  on  the  right.  The 
pylorus  has  a  sphincter  muscle  which  can  completely  close 
the  orifice.  The  stomach  is  followed  by  the  long  intestines 
(In),  most  of  which  have  been  removed,  leaving  a  short 
piece  in  front.  The  posterior  portion  of  the  intestine  is 
somewhat  dilated,  is  called  the  colon,  and  passes  into 
the  wide  terminal  rectum  (Rec).  The  whole  abdominal 
portion  of  the  intestinal  canal  is  suspended  from  the  me- 
dian dorsal  line  by  a  thin  membrane,  the  mesentery,  which 
forms  several  folds,  the  most  striking  of  which  is  the  omen- 
turn  or  grand  epiploon  (Om.).  This  fold,  when  in  situ, 
hangs  down  from  the  stomach  like  an  apron,  covering  over 
the  intestines  ventrally.  Upon  opening  the  walls  of  the 
abdomen,  it  is  the  first  structure  met  with.  It  usually  con- 
tains a  great  deal  of  fat.  Its  principal  function  is  supposed 
to  be  to  prevent  the  loss  of  heat.  The  omentum  is  present  in 
all  mammals,  but  is  least  developed  in  Cetaceans,  being  most 
prominent  in  Carnivora  and  ruminants.  Connected  with 
the  intestine  are  two  glands,  the  liver  (Li)  and  pancreas. 
The  liver  is  large  and  lies  directly  underneath  the  diaphragm. 
The  elongated  light-colored  pancreas  lies  alongside  the  front 
end  of  the  intestine  (In),  or  so-called  duodenum ;  in  its 
microscopic  structure  it  resembles  the  salivary  glands.  The 
spleen  is  closely  connected  with  the  stomach,  and  is  of  an 
elongated  shape,  as  in  the  majority  of  the  Mammalia  mono- 
delphia. 

The  kidneys  (Ki)  are  large  and  oval,  and  lie  on  either 
side  of  the  vertebral  column ;  the  aorta  passes  between 
them,  giving  off  a  renal  branch  to  each  gland.  A  deli- 
cate ureter  ( Urt)  passes  from  each  kidney  obliquely  across 
the  rectum  to  the  large  flask-shaped  bladder  (Bl).  A 
urethra  (Ur)  arises  from  the  bladder  posteriorly  and 


506  ZOOLOGY. 

opens  in  the  female  immediately  below  the  anus,  but  in  the 
male  enters  the  penis. 

The  ovary  (Ov)  is  small  and  is  placed  near  the  open  end 
of  the  oviduct  or  Fallopian  tube,  which  can  be  seen  in  the 
figure  extending  alongside  the  rectum  above  the  bladder. 
The  two  oviducts  (Ovd)  unite  posteriorly  to  form  the  uterus 
(Ut). 

Fig.  492,  II.,  is  a  median  longitudinal  section  of  the  brain. 
The  spinal  cord  passes  into  the  medulla  oblongata  (M),  over 
which  lies  the  large  cerebellum  (Cb),  and  the  small  corpora 
quadrigemina  (Q).  In  front  is  the  large  cerebrum  (C)  and 
the  small  olfactory  lobe  (L).  Tig.  492,  III.,  is  a  diagram  of 
the  eye  (see  explanation  of  the  figure). 

By  carrying  the  dissection  further,  the  student  will  be  able 
to  examine  the  tongue  with  its  papillae  ;  the  epiglottis  at 
the  back  of  the  mouth  in  front  of  the  trachea  ;  the  larynx, 
a  peculiarly  modified  portion  of  the  trachea  in  the  neck, 
with  two  elastic  bands  stretched  across  its  interior  ;  the 
bands  or  vocal  cords  may  be  set  in  vibration  by  a  blast  of 
air  from  the  lungs.  The  heart  may  also  be  dissected  fur- 
ther to  find  the  origin  of  the  pulmonary  vessels,  and  to 
make  out  the  four  divisions  or  chambers.  (Minot.) 

The  eggs  of  mammals  are  exceedingly  minute,  partly  owing 
to  the  small  quantity  of  yolk  in  them  ;  the  eggs  of  the  few 
which  have  been  examined  are  about  a  quarter  of  a  milli- 
metre (TJ^ — J--J-J-  inch)  in  diameter.  In  the  duckbill  the  egg 
is  large  and  with  more  yolk,  like  those  of  birds,  being  about 
five  millimetres  in  diameter.  Mammals  are  divided  into 
non-placentals  and  placentals,  according  as  the  embryos  are 
surrounded  or  not  with  &  placenta  or  "  after-birth."  This 
organ  is  a  development  of  the  allaritois,  serving  as  a  means 
chiefly  of  nutrition,  being  filled  with  blood-vessels  leading 
from  the  walls  of  the  womb  of  the  parent,  and  also  acting 
as  an  organ  of  respiration,  and  to  carry  off  the  effete  pro- 
ducts by  means  of  the  maternal  circulation. 

Mammals  may  be  born  helpless  and  only  partly  developed, 
as  in  the  Marsupials  ;  or  capable  of  locomotion  and  sucking 
milk,  as  in  the  calf  or  colt ;  or  helpless  for  many  months, 
as  in  human  infants.  The  changes  in  the  form  of  the  body 
after  birth  are  much  less,  on  the  whole,  than  in  the  birds. 

The  sexes  differ  externally  in  size  and   ornamentation. 


ANATOMY  OF  THE  OAT, 


507 


3      g         j~-s  P 


B«c     3«     is"     »!^VA?:'  / 
&o  cr     E-ffl      2,-S_,         V -".- -,*  .&• . /;•  -f 


568  ZOOLOGY. 

Darwin  calls  attention  to  the  fact  that  in  mammals  the  male 
wins  the  female  rather  by  the  law  of  battle  than  by  the  dis- 
play of  high  colors  and  attractive  ornaments.  During  the 
breeding  season,  desperate  contests  take  place  between  the 
rival  males  ;  even  the  males  of  the  timid  hare  will  at  such 
times  fight  until  the  weaker  is  killed  ;  so  moles,  squirrels, 
horses,  male  seals  and  male  sperm-whales,  whose  heads  are 
larger  than  in  the  female,  and  beavers,  will  fight  desperately. 
It  is  a  rule  that  the  males  of  such  animals  as  are  provided 
with  tusks  or  horns  always  fight  for  the  possession  of  the 
female.  It  is  so  with  bulls,  deer,  elephants,  boars,  and  rams  ; 
at  the  same  time  these  are  organs  of  defence  by  which  the 
males  protect  their  family,  flock,  or  herd.  On  the  other 
hand,  in  the  female  rhinoceros,  some  antelopes,  the  reindeer, 
as  opposed  to  the  other  deer,  some  sheep  and  goats,  etc.,  the 
horns  are  nearly  as  well  developed  as  in  the  opposite  sex. 
The  modes  of  attack  are  various  :  the  ram  charges  and 
butts  with  the  base  of  his  horns,  the  domestic  bull  gores 
and  tosses  any  troublesome  enemy,  while  the  Italian  buffalo 
"  is  said  never  to  use  his  horns  ;  he  gives  a  tremendous  blow 
with  his  convex  forehead,  and  then  tramples  on  his  fallen 
enemy  with  his  knees."  Darwin  also  says  that  male  quad- 
rupeds with  tusks  use  them  in  a  variety  of  ways  ;  thus  the 
boar  "  strikes  laterally  and  upward,  the  musk-deer  with 
serious  effect  downward,"  while  the  walrus  can  strike  either 
upward,  downward,  or  sideways  with  equal  dexterity. 

The  males  are  usually  larger  when  there  is  any  difference 
in  size  ;  this  is  seen  in  the  eared  seals,  especially  CallorJiinus 
ursinus,  in  the  ox,  Indian  buffalo,  and  the  American  bison, 
as  well  as  the  lion.  The  mane  of  the  latter  adds  to  its  ap- 
pearance of  greater  weight  and  bulk,  and  Darwin  says  that 
the  lion's  mane  "  forms  a  good  defence  against  the  one 
danger  to  which  he  is  liable — namely,  the  attacks  of  rival 
lions."  As  regards  distinctions  in  color,  male  ruminants 
are  most  liable  to  exhibit  them.  In  the  Derbyan  eland  the 
body  is  redder,  the  neck  much  blacker,  and  the  white  band 
separating  these  colors  broader  than  in  the  females.  In  the 
Cape  eland  the  male  is  slightly  darker  than  the  female.  In 
the  Indian  black-buck  the  male  is  very  dark,  almost  black, 


VOCAL  GROANS   OF  MAMMALS.  569 

while  the  female  is  fawn-colored  :  male  antelopes  are  blacker 
than  the  female.  The  Banteng  bull  is  almost  black,  while 
the  cow  is  of  a  bright  dun.  Among  the  lemurs  the  male  of 
Lemur  macaco  is  coal-black,  while  the  female  is  reddish  yel- 
low. The  sexes  of  monkeys  differ  much  in  coloration.  Cer- 
tain male  seals,  bats,  rats,  and  squirrels  have  brighter  colors 
than  in  the  opposite  sex.  On  the  other  hand,  the  female 
Rhesus  monkey  is  adorned  with  a  brilliant  red  naked  ring 
around  the  tail ;  this  is  wanting  in  the  male,  which,  how- 
ever, is  larger,  with  larger  canines,  more  bushy  whiskers 
and  eyebrows  ;  and  Darwin  states  that  in  monkeys  the  males 
usually  differ  from  the  females  in  "  the  development  of  the 
beard,  whiskers,  and  mane." 

The  vocal  organs  of  mammals  are,  in  general,  constructed 
on  the  same  type.  The  larynx  is  formed  by  a  modification 
of  the  uppermost  ring  of  the  trachea,  called  the  cricoid  car- 
tilage, to  the  anterior  and  dorsal  edges  of  which  two  arytenoid 
cartilages  are  attached,  while  a  V-shaped  thyroid  cartilage, 
open  behind,  is  attached  to  its  side.  The  vocal  cords,  which 
are  modified  folds  of  the  mucous  membrane  lining  the 
trachea,  are  stretched  between  the  arytenoid  and  thyroid 
cartilages,  the  slit  between  them  being  called  the  glottis, 
which  is  covered  by  the  epiglottis.  Thus,  in  mammals  the 
organs  of  voice  are  situated  almost  solely  at  the  upper  end 
of  the  trachea.  In  the  whales  the  vocal  chords  are  not  de- 
veloped. The  male  gorilla,  which  has  an  exceedingly  loud 
voice,  as  well  as  the  adult  male  orang  and  the  gibbon,  is 
provided  with  a  laryngeal  sac.  In  the  howling  monkey 
(Mycetes)  of  Brazil,  the  hyoid  apparatus  and  larynx  are  re- 
markably modified,  the  body  of  the  former  being  changed 
into  a  large  bony  drum  or  air-sac  communicating  with  the 
larynx.  The  vocal  organs  are  a  third  larger  in  the  males 
than  in  the  females.  "  The  males  begin  the  dreadful  con- 
cert, in  which  the  females,  with  their  less  powerful  voices, 
sometimes  join,  and  which  is  often  continued  during  many 
hours  "  (Darwin).  They  apparently  howl,  as  birds  sing, 
for  the  simple  pleasure  of  the  thing.  Apparently,  the  most 
musical  mammal,  man  excepted,  is  a  gibbon  (Hylobates 
agilis),  which  can  sing  "  a  complete  and  correct  octave  of 


570  ZOOLOGY. 

musical  notes  "  (Martin  ex  Darwin).  While  quadrupeds 
use  their  voices  as  alarm  calls,  most  of  the  sounds  are  pro- 
duced by  the  males,  especially  during  the  breeding  season. 

Animals  are  mutually  attracted  or  are  individually  pro- 
tected from  the  attacks  of  other  species  by  odors.  The 
scent-bags  or  odoriferous  glands  secreting  a  fluid  differing 
in  consistency  in  different  animals,  are  situated  near  the 
base  of  the  tail,  as  in  the  skunk,  polecat,  musk-deer,  civet- 
cat  and  allies,  or  they  may  be  developed  in  the  side  of  the 
face,  as  in  the  male  elephant,  as  well  as  sheep  and  goats. 
The  odor  is  either  of  musk  or  some  form  of  it.  The  shrew- 
mice,  by  reason  of  their  odoriferous  glands,  are  disliked  and 
consequently  not  hunted  by  birds.  Universal  deference  is 
paid  to  the  skunk  ;  few  dogs,  and  only  those  which  are  in- 
experienced or  peculiarly  gifted,  attacking  them.  The 
males  more  usually  emit  a  stronger  odor  than  those  of  the 
opposite  sex. 

Some  mammals  have  a  summer  and  a  winter  pelage.  The 
hare,  at  the  beginning  of  winter,  doffs  its  summer  coat  for  a 
suit  of  white.  The  hibernation,  or  winter-sleep,  is  a  re- 
markable feature  in  the  life  of  quadrupeds  living  in  the 
north  temperate  zone,  such  as  the  bear,  dormouse,  and  bats. 
During  this  period  the  temperature  of  their  body  falls, 
respiration  and  circulation  are  lowered  in  the  one  case  or 
nearly  ceases  in  the  other,  and  life  is  sustained  by  the  ab- 
sorption of  fat,  which  accumulates  on  the  under  side  of  the 
neck  in  the  so-called  hybernation-glands. 

There  are  about  3500  species  of  mammals  described,  of 
which  2100  are  living  ;  of  these  310  inhabit  America  north 
of  Mexico.  Mammals  live  all  over  the  earth's  surface,  but 
mostly  in  the  tropical  region,  those  of  the  arctic  zones  having 
been  derived  from  the  south  since  the  end  of  the  Tertiary 
period.  The  range  in  space  of  certain  species  is  very  great — 
for  example,  the  cougar,  panther,  or  puma  ranges  from  Brit- 
ish to  South  America  (Chili).  The  mammalian  fauna  of  the 
Tertiary  deposits  of  the  west  was  far  more  abundant  than  now, 
the  remains  of  over  five  hundred  species  having  been  already 
discovered  by  Leidy,  Cope,  and  Marsh  in  the  few  spots  ex- 
amined. The  earlier  (Eocene)  mammals  were  generalized 


ORIGIN  OF   DOMESTIC  MAMMALS.  571 

forms,  combining  in  a  remarkable  degree  characters  more 
elaborated,  and  in  great  detail,  in  different  orders  of  living 
mammals,  especially  the  Ungulates.  For  example,  from  the 
Eocene  Coryphodon,  a  generalized  ungulate  animal,  have 
probably  been  derived  the  ruminants,  the  tapirs,  hog,  hip- 
popotamus-like forms,  the  rhinoceros,  and,  finally,  the 
horse.  This  inference  is  based  on  the  fact  that  the  bones 
and  teeth  of  Corypliodon  present  characters  which  are  no 
longer  combined  in  any  one  species  of  mammals,  but  which 
are  found  worked  out  in  detail  in  the  members  of  the  differ- 
ent orders  referred  to. 

Moreover,  the  early  Tertiary  mammals  had  brains  much 
smaller  than  in  any  existing  forms,  and  with  only  one  ex- 
ception, without  convolutions — showing  that  the  develop- 
ment of  the  size  of  the  brain  and  its  convolutions,  and  con- 
sequently of  the  intellect.,  has  kept  pace  with  the  successive 
stages  in  the  specialization  shown  in  existing  forms,  and 
which  agree  with  the  increasing  complexity  of  the  Ameri- 
can Continent  and  the  subdivision  of  the  western  part  of 
the  continent  into  distinct  basins,  with  separate  mountain 
systems  and  river- valleys.  The  result  of  all  this  apparent 
waste  of  generalized  forms,  and  the  survival  of  the  few 
favored  types  now  existing,  has  been  the  preservation  of 
animals  which  have  been  domesticated  by  man,  such  as  the 
dog,  pig,  horse,  ox,  camel,  elephant,  and  of  others  useful  as 
food  or  as  intelligent  servants  ministering  to  his  every-day 
wants. 

The  earliest  mammals  were  small  insectivorous  or  gnaw- 
ing marsupials,  none  larger  than  a  cat,  and  first  appearing 
in  Jurassic  strata. 

The  Mammalia  are  divided  into  three  sub-classes — viz.,  the 
Ornithodelphia  (duckbill  and  Echidna),  the  Didetyliia  or 
marsupials,  and  the  Monodelpliia,  comprising  all  the  higher 
mammals. 

Sub-class  1.  OrnithodelpUa. — The  duckbill  and  spiny  ant- 
eater  (Fig.  493,  Echidna  hystrix)  are  the  only  representatives 
of  the  sub-class,  of  which  there  is  but  a  single  order,  called 
Monotremes,  and  are  distinguished  by  the  following  char- 
acters. The  oviducts,  vasa  deferentia  and  ureters,  open  into 


572 


ZOOLOGY. 


the  cloaca,  as  in  birds.  The  sternum  is  provided  with  a  pecu- 
liar T-shaped  bone,  and  there  are  important  features  in  the 


<•**=; 


(- 


s^^M>  'Mi* 

^5==-.  . ^ -^'\  \=^V,\      i    i    >4        i 

r 


brain  separating  them  from  the  members  of  the  higher  sub- 
classes.    There  are  several  characters  allying  them  to  the 


DUCKBILL  AND  ECHIDNA. 


573 


birds  and  reptiles,  and  besides  those  mentioned  one  of  the 
most  obvious  is  the  long,  toothless  jaws  (there  are  eight 
horny  teeth  in  the  duckbill),  which  are  long  and  narrow  in 
the  Echidna,  or  broad  and  flat  in  the  duckbill  (Ornithor- 
Tiynclms  paradoxus  Blumenbach),  where  it  is  covered  by  a 
leathery  integument ;  the  external  ear  is  wanting. 


Fig.  494.— Skeleton  of  Echidna  hyslrix.—Yrom.  Brehm's  Thierlebeu, 

In  the  aquatic  duckbill  the  feet  are  webbed,  with  claws 
of  moderate  size.  It  is  covered  with  a  soft  fur,  and  is  about 
half  a  metre  (17-22  inches)  long.  Its 
habits  arc  like  those  of  a  muskrat,  fre- 
quenting rivers  and  pools  in  Australia 
and  Van  Dieman's  Land,  sleeping  and 
breeding  in  holes  extending  from  un- 
der the  water  up  above  its  level  into 
the  banks,  and  with  an  outlet  on  shore. 
It  lives  on  mollusks,  worms,  and 
water-insects.  Young  duckbills,  five 
cm.  long,  have  been  found  in  their 
nests. 

The  spiny  ant-eater  (Figs.  493  and 
494)  is  represented  by  three   species, 
the  Echidna  liystrix  Cuvier,  of   Aus- 
tralia, E.  Laivesii  Ramsay,  from  Port 
Moresby,  New  Guinea,  also  by  a  re- 
cently  discovered  form  inhabiting  the 
elevated    portions   of    Northern    New  marsupial  bones. 
Guinea,  and  called  by  Gervais  Acanthoglossus  Bruijnii.    In 
these  singular  animals  the  bill  is  long  and  slender,  tooth- 


574  ZOOLOGY. 

less,  while  the  palate  is  armed  with  rows  of  strong,  sharp 
spines  ;  the  tongue  is  long  and  slender,  like  that  of  the  ant- 
eater,  while  the  body  is  armed  with  quills  like  those  of  a 
porcupine  ;  the  claws  are  very  large  and  strong,  adapted  for 
tearing  open  ant-hills.  All  the  species  are  from  one  third 
to  one  half  of  a  metre  (12-19  inches)  in  length. 


Pig.  496.— Skeleton  of  the  Kangaroo.— From  Brehm's  Thierleben. 

Sub-class  2.  Marsupialia. — These  are  singular  forms,  rep- 
resented by  the  opossum  in  this  country,  and  the  kangaroo, 
with  a  number  of  other  forms,  in  Australia.  They  differ 
from  all  other  mammals  in  having  a  pouch  (marsupium)  for 
the  reception  of  the  young  immediately  upon  birth,  where 


MARSUPIALS. 


575 


they  are  attached  to  the  nipples  at  the  bottom  of  the  pouch. 
This  large  pouch  (absent  in  some  opossums  and  in  the 
Dasyuridm)  is  supported  by  two  long  slender  bones  attached 
to  the  front  edge  of  the  pelvis  and  projecting  forward  (Fig. 
495  m  and  Fig.  497). 

In  Thylacinus,  the  Tasmanian  wolf,  these  bones  are  car- 
tilaginous. In  the  opossum,  the  kangaroo,  and  probably 
most  marsupials,  the  young  remains  in  the  pouch  attached 
to  the  nipple,  which  fills  the  mouth.  "  To  this  it  remains  at- 
tached for  a  considerable  period,  the  milk  being  forced  down 
its  throat  by  the  contraction  of  the  cremaster  muscle.  The 
danger  of  suffocation  is  avoided  by  the  elongated  and  coni- 
cal form  of  the  upper  extremity  of  the  larynx,  which  is  em- 
braced by  the  soft  palate,  as  in  the  Cetacea,  and  thus  respi- 
ration goes  on  freely, 
while  the  milk  passes, 
on  each  side  of  the 
laryngeal  cone,  into 
the  oesophagus " 
(Huxley).  In  the  car- 
nivorous forms  the 
brain  is  low  in  struc- 
ture, the  olfactory 
lobes  being  very  large, 
completely  exposed, 
while  the  cerebral 
hemispheres  are  small 
and  quite  smooth. 

The  dentition  of  marsupials  is  characteristic,  none  having 
three  incisor  teeth  upon  each  side,  above  and  below,  and 
none  but  the  wombat  (Phascolomys),  with  an  equal  num- 
ber of  incisors  in  each  jaw,  there  being  usually  more  in  the 
upper  than  in  the  under  jaw. 

The  lowest  marsupial  is  the  Tasmanian  wolf  (Thylacinus), 
which  is  rather  smaller  than  the  wolf.  The  Tasmanian  devil 
(Dasyurus  ur sinus  Geoffrey,  Fig.  383)  is  a  vicious,  trouble- 
some creature,  about  the  size  of  a  badger.  The  opossums 
inhabit  North  and  South  America.  They  have  a  long  tail 
and  a  plantigrade  step — i.e.,  they  walk  on  the  sole  of  the 
whole  foot.  The  Virginian  opossum  (Fig.  407.  Didclphys  Vir- 


Fi°-.  49?'.— Opossum  (from  Tenney's  Zoology)  and 
side  view  of  pelvis  with  the  marsupial  bone,  M. 


576 


ZOOLOGY. 


giniana  Shaw)  lives  chiefly  in  trees.  Lawson  says  that 
"  the  female  doubtless  breeds  her  young  at  her  teats,  for  I 
have  seen  them  stick  fast  thereto  when  they  have  been  no 


bigger  than  a  small  rasberry  and  seemingly  inanimate.  She 
has  a  paunch,  or  false  belly,  wherein  she  carries  her  young 
after  they  are  from  those  teats,  till  they  can  shift  for 


EDENTATE  MAMMALS.  577 

themselves.  Their  food  is  roots,  poultry,  or  wild  fruits. 
They  have  no  hair  on  their  tails,  but  a  sort  of  a  scale  or 
hard  crust,  as  the  beavers  have.  If  a  cat  has  nine  lives, 
this  creature  surely  has  nineteen  ;  for  if  you  break  every 
bone  in  their  skin  and  mash  their  skull,  leaving  them  for 
dead,  you  may  come  an  hour  after  and  they  will  be  gone 
quite  away,  or  perhaps  you  may  meet  them  creeping  away. " 
("  Perfect  Description  of  Virginia,"  1649.) 

There  are  squirrel-like  flying  marsupials  (Petaurus), 
marsupial  rats,  marsupial  bears,  and  marsupial  ant-eaters 
(Myrmecobius),  but  the  most  characteristic  Australian  ani- 
mals are  the  different  kinds  of  kangaroo  (Macropus  thetidis, 
Fig.  498). 

The  largest  species,  M.  giyanteus  Shaw,  is  1-8  metres,  or 
nearly  six  feet  long.  Kangaroos  go  in  herds,  and  move  by 
a  succession  of  long  leaps. 

All  marsupials  are  stupid,  low  in  intelligence,  and,  in  the 
insectivorous  and  carnivorous  forms,  of  vicious  temper. 
With  the  exception  of  the  opossums,  all  are  confined  to  Aus- 
tralia, New  Zealand,  and  New  Guinea. 

Sub-class  3.  Monodelphia. — While  in  the  marsupials  the 
termination  of  the  oviduct  is  double,  in  the  present  group 
it  is  always  single,  whence  the  name  Monodelphia.  The 
members  of  the  group  are  also  called  placental  Mammalia, 
because  the  young  at  birth  are  of  considerable  size  and 
nearly  perfect  in  development,  being  nourished  until  born 
by  a  highly  vascular  mass  or  thick  membrane  (placenta) 
supplied  with  arteries  and  veins,  developed  originally  from 
the  allantois,  which  is  a  temporary  embryonic  membrane. 
The  brain,  as  a  rule,  presents  an  advance  over  that  of  any 
of  the  preceding  mammals,  the  corpus  callosum  being  better 
developed,  while  the  anterior  commissures  are  all  reduced. 
There  are  no  marsupial  bones,  though  in  some  Carnivora 
certain  small  cartilages  appear  to  represent  them. 

There  are  twelve  orders,  as  follows  : 

Order  1.  Bruta  or  Edentata. — These  creatures,  repre- 
sented by  the  sloths,  ant-caters,  pangolins,  and  armadillos, 
stand  next  above  the  non-placentals  or  marsupials,  as  the 
brain  is  but  little  better  developed,  the  hemispheres  in  some 


578 


ZOOLOGY. 


forms  being  nearly  smooth,  while,  in  point  of  their  general 
structure  and  intelligence,  they  stand  at  the  foot  of  the  sub- 
class. The  teeth  may  be  entirely  undeveloped,  as  in  the 
common  ant-eater,  but  when  developed  they  are  not  encased 


in  enamel.  In  most  Edentates  the  incisors  are  absent,  but 
the  lateral  one  may  exist  in  the  armadillo  (Dasypus).  The 
feet  are  formed  for  grasping  or  digging,  and  end  in  large 
straight  or  curved  claws.  They  are  either  hairy  or  pro- 


SLOTHS  AND    THEIR  ALLIES. 


579 


tected,  as  in  the  pangolins  (Fig.  501)  and  armadillos  (Fig. 
502),  with  large  thick  scales.  They  feed  on  insects  and  de- 
cayed animal  matter,  or  on  leaves.  They  are  of  moderate 
size,  though  certain  extinct  forms  were  colossal  in  stature. 

The  leaf-eating  forms,  viz.,  the  sloths,  differ  from  the 
other  Bruta  in  the  very  long  and  slender  ^mbs,  the  hinder 
pair  the  shorter.  There  are  five  teeth  above  and  four  below, 
which  become  sharp  with  use,  like  chisels  ;  the  stomach  is 
said  to  be  remarkably  complex.  In  disposition  these  crea- 
tures are  types  of  sluggishness  ;  they  live  in  trees,  being 
absolutely  helpless  on  the  ground,  not  being  capable  of 
walking  on  the  bottom  of  the  foot. 

Waterton  says  that,  in  climbing,  the 
ai  (Brady pus  tridaclylus,  Figs.  499  and 
500)  uses  its  legs  alternately  ;  that  its 
hair  "  is  thick  and  coarse  at  the  ex- 
tremity and  gradually  tapers  to  the 
root,  where  it  becomes  fine  as  a  spider's 
web.  His  fur  has  so  much  the  hue  of 
the  moss  which  grows  on  the  branches 
of  the  trees,  that  it  is  very  difficult  to 
make  him  out  when  he  is  at  rest." 

None  of  the  Edentates  now  occur  in 
the  United  States,  but  formerly  colos- 
sal, sloth-like  forms,  with  some  resem- 
blance to  the  ant-eaters,  ranged  over 
the  Southern  and  Middle  States  as  far 
north  as  Pennsylvania,  their  bones  oc- 
curring in  caves.  Such  was  the  Megatherium,  a  gigantic, 
sloth-like  creature,  which  extended  from  Pennsylvania  to 
the  pampas  of  South  America,  and  whose  skeleton  is  over 
five  metres  (18  feet)  long.  With  it  was  associated  the  Meg- 
alonyx,  first  described  by  Thomas  Jefferson  ;  it  was  as  large 
as  a  bison,  as  was  the  Mylodon.  These  animals  walked  on 
the  soles  of  the  feet,  could  rise  on  their  hind  legs  and  partly 
support  themselves  by  their  thick  tails,  pulling  down  large 
trees  and  feeding  upon  the  leaves  and  smaller  branches. 

In  the  ant-eaters  the  jaws  are  toothless,  but  very  long,  and 
the  tongue  is  of  great  length  and  very  extensile  ;  the  sub- 


Fig.  500.  — Ai,  or  Three- 
toed  Sloth,  in  its  natural  atti- 
tude.—After  Wood,  from 
Waterton. 


580 


ZOOLOGY. 


maxillary  glands  are  very  large,  so  that  the  viscid  salivary 
fluid  is  very  abundant.  They  burrow  into  ant-holes,  thrust- 
ing the  tongue  among  the  ants,  which  stick  in  multitudes  to 
the  viscid,  writhing  rod,  and  are  withdrawn  into  the  mouth. 
The  pyloric  end  of  the  stomach  is  gizzard-like.  The  ant- 
eaters  (Myrmecopliaga)  inhabit  South  America. 

The  pangolins,  or  species  of  Manis,  are  mail-clad  ant- 
eaters,  the  body  and  long  tail  being  covered  with  large 
overlapping  scales.  When  molested  they  roll  up  the  body. 
In  walking  the  hind  feet  rest  on  the  soles,  while  the  fore- 
feet are  supported  by  the  upper  side  of  the  long  bent 
claws. 


Fig.  501.— Pangolin  (Manis  longicaudata)  robbing  white  ant-nests.— After  Monteiro. 

The  long-tailed  pangolin  of  the  West  Coast  of  Africa  (Fig. 
501)  tears  open  with  its  long  claws  the  nests  of  the  white 
ants.  It  is  nearly  f  metre  (28-30  inches)  in  length. 

The  armadillos  (Fig.  502)  are  small  mammals  covered  with 
a  carapace,  consisting  of  from  three  to  thirteen  transverse 
rows  of  movable  scales  ;  by  rolling  into  a  ball,  these  singu- 
lar creatures  become  thoroughly  protected  from  their  ene- 
mies. Dasypus  novem-cinctus  Linn,  is  much  like  the  Peba 
armadillo,  and  extends  from  South  America  to  Texas.  The 
strange  extinct  armadillo-like  Glyptodon  of  South  Amer- 
ica, which  was  over  two  metres  (8  feet)  long,  was  covered 


THE  ARMADILLO. 


581 


by  a  heavy,  solid  coat-of-mail  consisting  of  polygonal  plates 
soldered  together  immovably. 

The  three  following  orders  have  by  most  authors  been 
placed  near  the  Primates  (monkeys,  etc.),  but  Owen,  from 


the  characters  afforded  by  the  brain,  has  shown  that  they  be- 
long at  or  near  the  bottom  of  the  scale.  Gill  has  shown 
that  not  only  by  the  brain,  but  by  other  characters  corre- 
lated with  the  low  development  of  the  brain,  the  Rodents, 


582  ZOOLOGY. 

Insect! vora,  and  bats  should  be  associated  with  the  Edentates 
in  Bonaparte's  division  (or,  as  Gill  terms  it,  super-order) 
of  IneducaUlia  (which  corresponds  to  Owen's  sub-class 
Lissencepliala}.  In  these  four  orders,  then,  the  cerebrum  is 
small,  smooth,  with  none  or  few  convolutions  ;  in  front 
it  does  not  cover  the  olfactory  lobes,  and  behind  leaves 
the  cerebellum  wholly  or  partly  uncovered. 

On  the  other  hand,  in  the  super-order  Educdbilia,  com- 
prising the  following  orders  :  Cetacea,  Sirenia,  Proloscidia, 
Hyracoidea,  Toxodontia,  Ungulata,  Ferce,  and  Primates, 
the  brain  has  a  relatively  large  cerebrum,  behind  overlap- 
ping much,  or  all,  of  the  cerebellum,  and  in  front  much,  or 
all,  of  the  olfactory  lobes  (Gill).  The  cerebrum  is  also  con- 
voluted ;  the  convolutions  increasing  in  number  and  com- 
plexity, until  we  reach  the  apes  and  man,  and  accompanied 
by  increasing  intelligence  and  capability  for  mental  im- 
provement. Other  important  characters  are  mentioned  by 
Owen  and  by  Gill  in  support  of  this  arrangement. 

In  the  smooth  small  cerebrum,  as  well  as  in  other  re- 
spects, the  Ineducabilia  are  related,  together  with  the  mar- 
supials and  duckbill,  to  the  birds  and  reptiles.  In  the 
cloaca,  the  convoluted  trachea,  the  long,  slender,  beak-like, 
toothless  jaws  and  the  gizzard  of  the  ant-eaters,  the  quills 
of  the  porcupine  and  hedge-hog,  the  prov-entriculus  or  crop 
of  the  dormouse  and  beaver,  in  the  growing  together  of  the 
three  chief  metatarsals  of  the  jerboa,  as  in  birds,  in  the  keeled 
sternum  and  wings  of  the  bats,  there  are  points  of  resem- 
blances to  birds.  Owen,  whom  we  have  quoted,  also  adds 
the  aptitude  of  the  bats,  insectivores  and  certain  rodents 
"  to  fall,  like  reptiles,  into 'a  state  of  torpidity,  associated 
with  a  corresponding  faculty  of  the  heart  to  circulate  car- 
bonized or  black  blood." 

However,  there  are  points  in  which  these  orders  are  re- 
lated to  the  lemurs  and  monkeys. 

Order  2.  Glires.  (Rodentia.)— The  rats,  squirrels,  por- 
cupine, and  beaver  are  common  examples  of  this  extensive 
group.  They  differ  from  other  orders  in  the  large  incisors, 
the  dental  formula  of  which  is  normally  f  (|  in  Leporidce 
and  Laywnyidije},  and  in  the  absence  of  canine  teeth.  The 


ORDER  OF  RODENT8. 


583 


condyles  of  the  lower  jaw  are  longitudinal,  not  received  in  spe- 
cial glenoid  sockets, but  gliding  freely  backwards  and  forwards 
in  longitudinal  furrows.  The  feet  are  adapted  for  walking 
and  climbing  or  burrowing,  the  claws  being  well  developed. 
A  peculiarity  in  the  incisors  is  that  they  grow  out  as  fast  as 
they  are  worn  down  ;  this  is  due  to  the  fact  that  the  pulp  is 
persistent ;  the  enamel  in  front  causes  them  to  wear  away 


Fig.  503.— American  Flying  Squirrel  (Sciurapterus  volucella). 

behind  so  that  they  are  chisel-shaped.  The  species  are  pro- 
lific, live  mostly  on  vegetable  food,  and  are  of  small  size ; 
the  muskrat,  beaver,  and  capybara  being  the  largest  mem- 
bers of  the  group,  The  flying  squirrels  (Fig.  503)  take 
short  flights  by  means  of  the  expansion  of  the  skin  between 
the  fore  and  hind  legs.  The  Norway  lemmings  are  notice- 
able for  their  remarkable  migrations  from  the  elevated 


584  ZOOLOGY. 

plateaus  of  Scandinavia  down  arid  into  the  sea ;  the  object 
and  origin  of  which  are  inexplicable,  and  are  not  indicative 
of  much  intelligence.  From  this  and  their  nest- building 
habits,  rodents  are,  as  a  rule,  not  unlike  birds  ;  and  Owen,  for 
these  reasons,  ascribes  to  them  a  low  degree  of  intelligence. 
Granting  that  this  is  the  case,  an  exception  to  this  rule  is 
seen  in  the  social  beavers,  which  evince  a  high,  exceptional 
degree  of  intelligence.  Beavers  build  a  dam  in  a  running 
stream  so  as  to  create  an  artificial  pond  as  a  refuge  when  at- 
tacked, as  well  as  a  subaquatic  entrance  to  their  lodges  and  to 
their  burrows  in  the  banks  of  the  streams  they  inhabit.  Bea- 
ver dams  are  built  at  first  by  a  single  pair  or  family,  and  are 
added  to  from  year  to  year,  and  afterwards  maintained  for 
centuries  by  constant  repairs.  They  are  built  of  sticks  and 
mud,  usually  curve  up  stream,  with  a  sloping  water-face. 
Beavers  lay  up  stores  of  wood  for  winter  use  in  the  autumn ; 
they  can  gnaw  through  trees  eighteen  inches  in  diameter ;  they 
work  mostly  at  night.  They  often  construct  artificial  canals 
for  the  transportation  of  the  sticks  of  wood  to  their  lodges. 
This,  in  the  opinion  of  Mr.  Morgan  "is  the  highest  act  of 
intelligence  performed  by  beavers."  When  ponds  do  not 
reach  hard-wood  trees  or  ground  in  which  they  can  burrow 
for  safety,  they  will  build  canals  with  dams,  and  so  excavate 
them  that  they  will  hold  the  surface  drainage.  Morgan 
describes  one  canal  about  161  metres  (523  feet)  long  which 
"served  to  bring  the  occupants  of  the  pond  into  easy  con- 
nection, by  water,  with  the  trees  that  supplied  them  with 
food,  as  well  as  to  relieve  them  from  the  tedious,  and  per- 
haps impossible,  task  of  moving  their  cuttings  five  hundred 
feet  over  uneven  ground,  unassisted  by  any  descent. "  Bea- 
vers, in  swimming,  use  their  tail  as  a  scull,  and  the  hind 
feet  being  webbed,  its  propelling  power  while  swimming  is 
very  great.  They  carry  small  stones  and  earth  with  their 
paws,  holding  them  under  the  throat,  and  walking  on  their 
hind  feet.  They  use  the  tail  in  moving  stones,  working  it 
under  so  as  to  "  give  it  a  throw  forward."  Beavers  are  very 
social,  working  together  and  storing  up  wood  in  common. 
'  A  beaver  family  consists  of  a  male  and  female,  and  their 
offspring  of  the  first  and  second  years,  or  more  properly, 


HABITS  OF  THE  BEAVER. 


585 


under  two  years  old.     The  females  bring  forth  their  young 

from  two  to  five  at  a  time,  in  the  month  of  May,  and  nurse 

them  for  a  few  weeks, 

after  which  the  latter 

takes  to  bank."     They 

attain  their  full  growth 

at  two   years   and   six 

months,  and  live  from 

twelve  to  fifteen  years.  * 

Allied  to   the  beaver,          FlG.  504.— Sewellel  or  Showt'l.    Much  reduced. 

but  forming  the  type 

of  a  distinct  family,   is  the  singular    sewellel  or  showt'l 


Fig.  505.— Alpine  Hare  of  the  Rocky  Mountains.— After  Hayden. 

(Haplodon  rufus  Coues,  Fig.  504)  of  the  mountains  of  west- 
ern Oregon  and  Washington  Territory.     It  is  nearly  as  large 

*  The  American  Beaver  and  his  Works.     By  Lewis  H.  Morgan.      1 868. 


586 


ZOOLOGY. 


as  a  muskrat,  is  nocturnal  in  its  habits  and,  therefore,  rarely 
seen,  and  burrows  in  the  earth,  feeding  on  roots. 

The  lowest  in  intelligence  are,  perhaps,  the  hares,  rep- 
resented by  the  common  varying  hare  (Lepus  America- 
nus  Erxleben,  Fig.  505),  of  which  an  interesting  variety, 
L.  Bairdii,  lives  on  the  Alpine  summits  of  the  Rocky  Moun- 


Fig.  506.— The  Spalax  or  Blind  Rat.— After  Owen. 

tains.  The  largest  of  all  existing  rodents  is  the  Capy- 
bara  of  South  America,  which  looks  like  a  pig.  This  is 
succeeded  by  the  porcupine,  which  either  lives  in  trees  or 
burrows  in  the  earth,  while  the  more  intelligent,  active 
forms  are  the  beaver,  muskrat,  the  European  blind  rat 
(Spalax,  Fig.  506)  the  rats  and  mice,  squirrels,  and  lastly 

the  marmots.  The  domes- 
tic mouse  and  the  two  rats, 
the  brown  or  Norway  rat 
(Mus  decumanus  Pallas), 
the  black  rat  (Mus  rattus 
Linn.),  and  the  common 
house  mouse  (Mus  muscu- 
lus  Linn.),  are  cosmopoli- 
tan animals.  The  jumping 
mouse  (Fig.  507)  has  remarkably  long  hind  legs  and  short 
fore  legs.  Peculiar  to  the  western  plains  is  the  prairie-dog, 
(Cynomys  ludovicianus)  which  represents  the  marmots  of 
the  Old  World  ;  it  is  semi-social  and  takes  in  perforce  as 
boarders  the  owl  and  rattlesnake,  which  devour  its  young. 


Pig.  507.— Jumping  Mouse  (Zapus 
sonius).—  From  Tennoy's  Zoology. 


hud- 


MOLES  AND  SHREWS. 


587 


Order  3.  InsecMvora. — In  the  moles  the  incisors,  the 
canines,  and  molars  are  well  developed,  and  the  molars  have 
the  crown  surmounted  by  conical  projections  called  cusps. 
The  fore  feet  are  plantigrade,  with  large  claws,  and  the  en- 
tire limb  is  short,  thick,  mus- 
cular, and  fossorial,/.e.,  adapted 
for  burrowing  in  the  soil  (Fig. 
508).  The  shrews  comprise 
the  smallest  mammals.  Nearly 
all  are  nocturnal,  burrowing 
under  the  surface,  and  never 
seen  by  day ;  consequently, 
their  eyes  are  small,  and  most- 
ly hid  under  the  fur ;  while  the 
ears  are  small  and  concealed  by 
the  hair. 

The  shrews  are  mouse-like, 
having  feet  of  the  normal  form, 
and  a  long  nose.     In  our  com- 
mon shrew  (Sorex  platyrliinus  Wagner,  Fig.  509),  the  nose 
is  long,  and  the  tail  shorter  than  the  head  and  body. 

The  genuine  moles  are   the  characteristic  forms  of  the 
order ;  the  most  peculiar  being  the  star-nosed  mole,  Condy- 


Fig.  508.— Bones  of  fore  leg  of  a 
Mole.  52,  the  cubital  scapula ;  53, 
humerus  ;  54,  ulna  ;  55,  radius. — Af- 
ter Owen. 


Fig.  509.— Common  Shrew.— After  Cones. 


lura  cristata  Linn.,  which  occurs  from  the  Atlantic  to  the 
Pacific  Ocean,  while  the  common  mole  (Fig  510)  is  abundant 
in  the  Eastern  United  States. 

A  flying  form  with  a  superficial  resemblance  to  the  bat,  and 


588 


ZOOLOGY. 


with  the  same  habit  of  sleeping,  head  downward,  holding  on 
by  its  hind  feet,  is  the  Galeopithecus  of  the  East  Indies. 
This  singular  creature  has  been  placed  among  the  lemurs 
by  some  authors.  G.  volans  Pallas  inhabits  Java,  Sumatra, 
Borneo,  and  Siam. 


Fig.  510.— Common  Mole  (Scalops  aquations  Linn.).— After  Coues. 

Order  4.  Chiroptera. — The  bats  form  a  well-circumscribed 
group  of  mammals,  very  distinct  from  any  other,  especially 
in  the  greatly jnodified  fore-limbs,  the  radius  and  ulna  being 
united,  and  the  second  to  the  fifth  metacarpal  bones  and 
phalanges  being  very  long  and  slender,  supporting  a  thin, 
leathery  membrane  or  skin,  extending  to  the  hind  legs,  and 
wholly  or  partly  enclosing  the  tail  ;  the  hind  toes  being,  how- 
ever, free,  as  when  at  rest  or  in  the  vegetarians  when  feeding, 
bats  hang  head  downwards,  holding  on  by  their  claws.  The 
sternum  is  slightly  keoled  for  the  attachment  of  the  mus- 
cles of  flight.  The  mammary  glands  are  pectoral.  In  other 
respects,  especially  the  dentition,  the  bats  resemble  the 
Insectivora.  The  form  of  the  teeth  differs  from  the  ordi- 
nary insectivorous  bats  in  those  which  live  on  fruit.  The 
vegetable-eating  or  fruit-eating  bats  have  a  superficial  resem- 
blance to  the  flying  lemurs  ;  and  because  their  mammse  are 
pectoral,  have  been  placed  next  to  the  Primates. 


HABITS  OF  BATS. 


589 


Bats  live  in  caves  and  in  the  hollow  of  trees  by  day ;  all 
hibernate  in  the  same  situations,  going  into  winter  quarters 
in  the  autumn,  and  reappearing  in  the  warm  twilight  of 
spring.  Though  the  eyes  are  small,  and  the  sight,  so  far  as 


Fig.  511.— Skeleton  of  a  fruit  bat  (Pteropsus).— After  Owen. 

we  know,  deficient  in  keenness,  they  show  wonderful  skill 
in  avoiding  objects  during  their  rapid  flight.  The  ears  are 
very  large,  and  in  the  vampires  the  nose  is  adorned  with 


590 


ZOOLOGY. 


sensitive,  leaf -like  growths  of  complicated  form.     The  vam- 
pires are  known  to  enter  houses,  and  suck  the  blood  from 


VVllale   8t>en  from  abov 


from  the   sidc- 


aqlnl  -  -          < 

fiin?«i  f  P  ;       i°f-e  ;  e°:  9xocC'Pital  ;  so,  snpraoccipital  ;  p,  parietal  ;  «,  squamosal  ;  /, 
Flower         Palatme;  •;'  JUSal  5  5A>  stylohyoicl  ;  bh,  basihyoicl  ;  th,  thyrohyoid.-After 


the  extremities  of  sleeping  persons,  who  awaken  to  find  their 
feet  covered  with  blood. 


CETACEANS. 


59i 


largest  bats  are  the  fruit  bats  or  flying  foxes  (Ptero- 
pus)  of  the  East  Indies  ;  one  species  of  which  expands  one 
and  a  half  metres  (nearly  five  feet)  from  tip  to  tip  of  the 
wings.  Our  commonest  species  is 
the  little  brown  bat,  Vespertilio 
sululatus  of  Say  ;  nearly  as  com- 
mon is  the  red  bat,  Atalapha  no- 
veboracensis  Coues. 

Order  5.  Cete  (Cetacea).—WQ 
now  come  to  the  Educabilia,  in 
which  the  brain  is  more  highly  de- 
veloped, and  begin  with  two  very 
aberrant  orders,  the  whales  and 
Sirenians,  in  which  the  body  is 
fish-like,  though  the  tail  is  hori- 
zontal ;  the  pelvis  and  hind  limbs 
are  wanting,  either  wholly,  or  mi- 
nute rudiments  may  be  present ; 
and  they  are  aquatic,  occasionally 
leaping  out  of  the  water,  but  usu- 
ally only  showing  the  dorsal  fin  or 
nose  when  at  the  surface  to  breathe. 

The  whales  and  porpoises  have 
a  large,  broad  brain,  with  numer- 
ous and  complicated  deep  convolu- 
tions. 

In  the  skull  (Figs.  512,  513)  the 
aperture  for  the  spinal  cord  (fora- 
men magnum]  is  entirely  posterior 
in  situation  and  directed  some- 
what upward.  The  lower  jaw  is 
straight,  with  no  ascending  ramus, 
the  narrow  condyles  being  situated 
at  the  end  of  the  jaw,  at  the  point  j 

V.TT  fV,rt  on/Trlo  /-vf  +1-,^  yaTvmo    whale,  longitudinal  section  snow- 
by  the  angle  ol  the  ramus  ing  th'e  refative  8ize  and  form  of 

mammals.       The  teeth  are    the   cranial   cavity,    m^maxilla ; 


5i3.-skuii  of  the  sperm 

e,  longitudinal    SCCtion  8I1OW- 

' 


n 


premaxiiia.-After  Flower. 


conical,  with  a  single  root,  but  are 

sometimes  wanting.     There  is  no  neck  ;  the  cervical  verte- 

brae are  sometimes  confluent,  forming  a  single  mass.     The 


592  ZOOLOGY. 

limbs  form  a  pair  of  paddle-like  appendages  just  behind  and 
under  the  head,  which  are  supported  by  short,  flattened 
limb-bones,  the  carpals  and  phalanges  often  separated  by  car- 
tilage ;  the  second  digit  being  composed  of  more  than  three 
phalanges.  There  are  two  mammae  situated  near  the  anus. 
The  external  nostrils  are  either  single  or  double,  and  are  sit- 
uated on  the  top  of  the  head  ;  they  are  modified  to  form  the 
spiracles  or  "  blow-holes ;"  certain  folds  of  the  skin  prevent 
the  water  from  entering  the  air-passages.  The  vapor  blown 
from  the  holes  does  not  consist  of  water,  but  of  the  mucus 
from  the  nostrils,  and  the  moisture  in  the  breath.  The 
blow-holes  vary  in  form  in  different  kinds  of  whales.  The 
"spout"  of  the  sperm-whale  issues  in  a  single  short 
stream  from  the  extreme  end  of  the  snout,  and  curls  over 
in  front  of  the  head;  that  of  the  fin-back  whale  forms 
a  single  column  of  vapor  about  ten  feet  high  ;  the  right, 
humpback  and  sulphur-bottom  whales  each  "blow"  in  a 
double  stream  which  is  directed  backward  toward  the  tail. 

Whales  are  rarely  over  fifty  feet  long ;  the  sperm-whale 
has  been  known  to  reach  a  little  over  twenty-three  metres 
(76  feet)  in  length,  but  Professor  Flower  questions  whether 
the  sperm-whale  frequently,  if  ever,  when  measured  in  a 
straight  line,  exceeds  a  length  of  sixty  feet.  The  largest  of 
all  whales,  as  of  all  existing  animals,  is  the  fin-back  or  ror- 
qual (Balcenoptera  loops),  which  sometimes  measures  thirty- 
four  metres  in  length.  The  smallest  Cetacea  are  the  por- 
poises. 

In  the  Mysticete  or  whalebone  whales,  the  teeth,  present  in 
the  embryo,  become  reabsorbed  into  the  gums  before  birth  and 
are  replaced  by  plates  of  whalebone  (Fig,  514),  three  hun- 
dred of  which  may  be  present  on  each  side  of  the  mouth. 
The  inner  edges  of  these  plates  have  projecting  fibres,  form- 
ing a  rude  strainer ;  these  whales  feed  on  small  pelagic  jelly- 
fish, molluscs  and  Crustacea,  by  taking  in  a  mouthful  of 
water,  and  then  pressing  the  tongue  against  the  roof  of  the 
mouth,  expelling  the  water  through  the  openings  between 
the  plates,  the  fibres  acting  as  a  strainer.  Three  thousand 
five  hundred  pounds  of  whalebone  have  been  obtained  from 
a  single  bow-head  or  Greenland  whale  (Balwna  mysticetus). 


THE  SPERM  WHALK 


593 


The  cachelot  or  sperm-whale  (Fig.  515)  has  an  enormous 
head,  and  is  without  the  power  of  smell.  Above  the  nasal, 
frontal,  and  maxillary  bones  are  cavities  filled  with  a  fatty 
fluid  called  spermaceti,  used  in  the  manufacture  of  candles, 
ointments,  and  cosmetics,  such  as  cold  cream.  A  large  sperm- 


Fig.  514. — Head  and  tongue  of  finback  whale,  Salwnoptera  (the  latter  (a)  swollen 
by  the  gases  of  decomposition) ;  b,  whalebone  plates. 

whale  will  yield  2500  kilograms  of  this  substance.  Another 
valuable  substance  is  ambergris,  a  morbid  product,  the  result 
of  injury  to  the  intestine  by  the  beaks  of  cuttle-fishes,  upon 
which  animals  the  toothed  whales  largely  prey.  It  is  a  kind 
of  bezoar  or  gall-stone,  fatty,  aromatic,  burning  with  a  clear 
flame.  It  is  composed  of  benzoic  acid,  united  with  chlorine, 
of  a  balsamic  substance,  and  ambrain.  It  is  used  in  making 
perfumes. 


Fig.  515.— Outline  of  the  cachelot,  showing  how  the  blabber  is  removed;  b,  the 
situation  of  the  "  case  ";  c,  the  jnnk ;  d,  the  bunch  of  the  neck  ;  h,  the  hump  ;  t,  th 
ridge  ;  *,  the  small  ;  X1,  the  tail  or  flukes :  between  the  oblique  dotted  kneg  are  the 
spiral  strips  or  blanket  pieces.— After  Beale,  from  Gill. 

But  the  chief  use  of  whales  is  the  oil  extracted  from  the 
fat  enveloping  the  body,  called  blubber  by  whalers.  The 
most  valuable  of  the  whales  is  the  Greenland  whale,  as  it 
contains  the  most  oil,  individuals  having  been  known  to 
yield  nearlv  three  hundred  barrels. 


594 


ZOOLOGY. 


The  whale-fishery  first  sprang  up  in  the  twelfth  century 
in  the  Bay  of  Biscay.  In  the  New  England  colonies  whales 
were  pursued  in  boats  from  the  shore.  In  1854  the  fishery 
culminated ;  since  then  it  has  decreased.  It  is  principally 
carried  on  by  Americans,  New  Bedford  being  now  the  lead- 
ing port  from  which  whalers  are  sent  out  to  the  Arctic 


Fig.  516,—Kogia  Flowtri.— After  Grayson,  from  Gill. 

regions  and  Behring's  Straits,  one  hundred  and  ten  vessels 
having  been  sent  out  in  1876  from  this  port. 

Closely  allied  to  Physeter  macrocephalus  Lacepede,  are 
the  pigmy  whales,  represented  on  the  Californian  coast  by 
Kogia  Floweri  Gill  (Fig.  516),  which  is  nearly  three  metres 


Pig.  517.— Skull  of    Callignathus  simus,  seen  from  the  side  and  from  below.— 
After  Owen. 

(nine  feet)  in  length,  with  a  conical  head .  In  Callignatlius 
simus  Owen  (Fig.  517)  the  skull  is  short  and  broad ;  it  is 
found  on  the  coast  of  Madras,  India. 

The  narwhale  (Monodon  monoceros  Linn.)  is  distinguished 
by  the  long,  spirally-twisted,  horn -like  tusk  of  the  male, 
formed  of  the  left  upper  incisor,  which  becomes  nearly  three 


SIRENIANS  OH  SEA-COWS.  595 

metres  long,  the  female  having  no  visible  teeth  ;  there  being 
two  rudimentary  incisors  which  never  appear  through  the 
gum.  It  ranges  from  Hudson's  Straits  to  the  Arctic  seas, 
having  formerly  been  seen  along  the  coast  of  Labrador.  To 
the  family  of  dolphins  and  porpoises  belong  the  white  whale 
or  Delphinapterus  leucas  Pallas,  which  ranges  from  the  Gulf 
of  St.  Lawrence  northward ;  the  grampus  ( Grampus  griseus 
Cuvier) ;  the  blackfish,  of  which  there  are  two  species,  one 
Globicephalus  melas  Trail,  ranging  north  of  New  York,  and 
one  G.  Irachypterus  Cope,  to  the  southward,  and  the  por- 
poises, of  which  the  most  common  on  our  coast  is  Phoccena 
bracliycium  Cope  ;  the  rarer  is  P.  lineata  Cope.  On  the 
coast  of  Labrador,  as  well  as  northward,  occurs  the  thrasher 
whale  or  killer  (Orca  gladiator  Gray)  which  has  large 
teeth,  and  a  high  dorsal  fin  ;  it  attacks  whales,  gouging  out 
the  flesh  from  their  sides.  Certain  fossil  whales  were  pigmies 
in  size ;  while  the  Zeuglodon  of  the  Alabama  Eocene  Ter- 
tiary beds,  was  an  enormous  serpent-like  whale,  which  must 
have  measured  over  seventy  feet  in  length. 

Order  6.  Sirenia.—  In  the  few  species  of  sea-cows  represent- 
ing this  order,  the  lower  jaw  is  more  as  in  other  mammals, 
having  well  developed  ascending  rami  and  normal  transverse 
condyles  and  coronoid  processes.  The  teeth  are  well  developed, 
both  incisors  and  molars,  the  latter  with  flattened  or  ridged 
crowns,  adapted  for  the  trituration  of  vegetable  food.  A 
neck  is  indicated ;  the  two  nostrils  are  situated  at  the 
upper  part  of  the  snout,  and  the  lips  are  beset  with  stiff 
bristles,  while  the  mammae  are  pectoral.  The  fore  limbs  are 
of  moderate  length,  with  five  well-developed  digits,  but  still 
fin-like  and  bent  at  the  elbow.  The  brain  is  narrow  com- 
pared with  that  of  cetaceans,  and  the  heart  is  deeply  fissured 
between  the  ventricles.  The  manatees  of  America  and  the 
dugong  of  Australia  and  India  (Fig.  518)  live  in  the  mouths  of 
large  rivers,  feeding  on  seaweeds,  aquatic  plants,  or  the  grass 
along  the  shore.  The  Florida  manatee  (Manatus  Ameri- 
canus  Desmarest)  grows  to  a  length  of  from  two  to  nearly 
three  metres.  It  ranges  from  Florida  to  the  Amazons,  where 
it  is  called  Vacca  marina  ;  it  ascends  the  river  as  far  as  Pebas, 
Peru,  and  is  killed  and  eaten,  its  flesh  resembling  beef. 


596 


ZOOLOGY. 


Steller's  manatee  (Rhytina  Stelleri)  was  in  the  last  century 
found  in  abundance  on  the  shores  of  Behring's  Island  on  the 
coast  of  Kamtchatka;  twenty-seven  years  afterwards  (in 
1768)  it  was  totally  exterminated  by  the  sailors,  and  only  a 
few  imperfect  bones  exist  at  St.  Petersburg.  This  is  the 


V 

largest  Sirenian  known  ;  it  was  over  six  metres  in  length. 
It  differed  remarkably  from  the  other  forms,  in  having  no 
teeth,  but  was  provided  with  a  very  large,  horny,  palatine 
plate,  and  a  corresponding  one  covering  the  enlarged  point 
of  union,  or  symphysis,  of  the  lower  jaws.  In  the  Tertiary 


THE  PROBOSCIDIANS. 


597 


Period  a  fossil  Sirenian  (Halitherium)  inhabited  the  shore* 
of  western  Europe. 

In  the  structure  of  the  skull,  their  dentition  and  their  her- 
bivorous habits  the  Sirenians  in  a  degree  connect  the  Ceta- 
ceans with  the  Ungulates. 

Order  7.   Proboscidia. — Only  two  representatives  of  this 
group  are  now  in  existence,  the  Asiatic  and  African  elephant, 
a  number  of  other  forms  having  become  extinct.     The  group 
is  well  circumscribed,  when  we  consider  the  living  species, 
but  in  the  early  (Eocene)  Tertiary  Period  there  existed  forms 
which  indicate  that  the  Proboscidians  and  Ungulates  had  a 
common    origin.      In 
the  elephants  the  up- 
per incisors  are  enor- 
mously developed, 
while  there  are  none 
in  the  lower  jaw. 
There   are  no  canine 
teeth,   while  the  few 
molars  are  large,  trans- 
versely ridged.    In  the 
elephants    the   ridges 
are     numerous,     the 
spaces   between  them 
filled     with     cement. 
The  young  mastodon 
has  cement  on  the  up- 
per   surface    of    the 
tooth ;   the  ridges  af- 
terwards become  free 
and    covered   with 
enamel.     A  peculiari- 
ty in  the  elephant's  skull  is  its  large  size,  the  brain  cavity 
being  very  small  in  proportion  to  the  bulk  of  the  skull  itself. 
To  give  lightness  to  what  would  be  otherwise  an  insupportable 
weight,  the  cranial  bones  contain   numerous  large  air-cells 
(Fig.  520).   Another  remarkable  feature,from  which  the  group 
takes  its  name,  is  the  trunk  or  proboscis,  a  long,  thick,  fleshy, 
flexible   snout,  growing  from   the   front  edge  of  the  nasal 


Fig.  519.— Skull  of  young  elephant ;  22,  premax- 
illary  bone  containing  the  root  of  the  tusk,  k;  15, 
nasal  bone  ;  7,  par'etal  bone  or  temporal  region  ; 
26,  molar,  zygomatic  arch  ;  i,  lower  jaw  ;  c,  upper 
jaw  ;  m,  molar  tooth  ;  21,  maxilla  ;  11,  frontal ;  g, 
squamosal. — After  Owen. 


598 


ZOOLOGY. 


bones  (Fig.  520,  a).  The  trunk  ends  in  a  finger-like,  highly 
sensitive  point,  below  which  are  situated  the  nostrils.  The 
brain  has  a  large  cerebrum,  with  numerous  convolutions,  but 
more  of  thw  cerebellum  is  exposed  than  in  any  of  the  succeed- 
ing orders  ;  in  this  respect  and  in  the  large  incisors  the  Pro- 
boscidians approach  the  Rodentia. 

In  the  nature  of  the  limbs,  especially  from  the  fact  that 
elephants  walk  on  their  toes,  a  relation  to  the  Ungulates  is 

indicated.  They  are 
five-toed,  but  the  dig- 
its are  represented  ex- 
ternally only  by  the 
five  broad,  shallow 
hoofs,  the  foot  being 
supported  by  thick, 
broad  pads.  The  legs 
are  almost  wholly  free 
from  the  body.  The 
placenta  is  zonary 
and  deciduate.  The 
skin  is  naked  in  the 
existing  elephants, 
but  the  extinct  mam- 
moth was  covered 
sparsely  with  hairs. 
Elephants  live  in 
herds,  browsing  on 
the  leaves  of  trees 
and  herbs.  They  at- 
tain a  height  of  from 
three  to  four  metres 
(10-12  feet).  The 
Asiatic  elephant  has  a  concave  forehead  and  small  ears,  while 
the  African  species  has  a  full,  rounded  forehead  and  large 
ears,  with  four  hoofs  on  the  fore  feet  and  three  on  the  hind 
feet,  the  Asiatic  elephant  having  one  more  hoof  on  each  foot. 
The  fossil  mammoth  (Elephas  primigenius  Blumenbach), 
which  was  contemporaneous  with  early  man,  was  not  much 
larger  than  the  existing  species.  Its  tusks,  however,  were  of 


Fig.  520.— Section  of  an  elephant's  skull,  showing 
the  small  size  of  the  brain  cavity  as  compared  to  the 
whole  skull,  and  the  numerous  large  air  cells,  v, 
posterior  nostrils ;  13,  cavity  of  the  nose  ;  a,  front 
opening  of  the  bony  nostrils,  to  the  edge  of  which 
the  trunk  is  attached. — After  Owen. 


MAMMOTH  AND  MASTODON. 


599 


great  size,  some  being  five  metres  long.  It  formerly  ranged 
in  herds  over  northern  Europe  and  Asia,  as  well  as  America, 
bones  occurring  under  swamps  in  the  Northern  and  Middle 
United  States.  A  carcass  frozen  in  the  ice,  with,  the  hair 
still  on,  was  discovered  near  the  mouth  of  the  Lena  Kiver  in 
Siberia.  A  pigmy,  extinct  Maltese  elephant  of  the  late  Ter- 
tiary Period  was  only  1.7  metres  in  height. 

The  Mastodon  was  characterized  by  having  incisors  in  both 
jaws  of  some  of  the  species.     The  mastodon  had  molars  with 


Fig.  521.— Dinotherium.— From  a  restoration  by  Brandt. 

conical  cusps,  and  was  3f-4  metres  (12-13  feet)  in  height. 
The  mastodon  (Mastodon  giganteum  Cuvier)  was  an  earlier 
type  than  the  elephant,  and  formerly  inhabited  the  North 
American  continent. 

In  the  Dinotherium  of  the  Middle  Tertiary  (Fig.  521)  there 
were  only  two  incisors,  and  they  grew  out  from  the  under 
jaw.  It  was  elephantine  in  its  form,  according  to  Brandt. 

Order  8.  Hyracoidea. — With  some  affinities  to  the  Eo- 
and  a  decided  resemblance  in  some  particulars  to 


600  ZOOLOGY. 

the  rhinoceros  among  the  Ungulates,  the  members  of  this 
small  order  are  in  general  characterized  by  having  long, 
curved  incisors ;  and  by  feet  provided  with  pads  as  in  Ro- 
dents and  Carnivora,  the  toes  being  encased  in  hoofs  (four  in 
front  and  three  behind).  The  Hyrax,  a  little  gregarious 
animal  living  in  holes  among  rocks,  of  which  there  are  two 
or  three  species  known,  one  South  African,  and  another  in 
the  Holy  Land  and  Arabia,  thought  to  be  the  coney  referred 
to  in  the  Bible,  is  the  only  genus. 

Order  9.  Toxodontia. — Of  this  group,  of  which  no  spe- 
cies are  now  living,  the  types  are  Toxodon  and  Nesodon. 
They  are  placed  by  many  authors  among  the  odd-toed  Ungiv 
lates,  not  far  from  the  tapirs.  Their  incisors  were  f-  or  f. 
Toxodon  in  its  skull  bore  some  resemblance  to  the  Sirenians, 
and  in  the  teeth  were  in  certain  respects  like  the  Edentates. 
The  species  lived  in  South  America  during  the  early  Tertiary 
Period. 

Order  10.  Ungulata. — The  larger  proportion  of  mammals 
belong  to  this  interesting  order,  which  comprises  nearly  all 
those  species  of  mammals  useful  to  man,  such  as  the  ox, 
camel,  pig,  deer,  and  horse.  They  are,  in  general,  charac- 
terized by  walking,  so  to  speak,  on  their  toes,  each  toe  being 
at  the  end  encased  in  a  horny  hoof  ;  not  more  than  four  toes 
being  completely  developed  on  a  foot.  The  teeth  are  usually 
well  developed,  with  six  incisors  in  each  jaw,  but  these  are 
often,  especially  in  the  upper  jaw  less  in  number  or  entirely 
absent,  as  in  the  sheep,  deer,  and  ox.  The  collar-bone  is 
absent.  The  brain  still  remains  small  compared  with  the 
bulk  of  the. skull,  and  the  intestinal  canal  is  of  unusual 
length  compared  with  that  of  animals  of  the  previous  orders. 

The  Ungulates  have  been  divided  by  Owen  into  two  sub- 
orders, according  to  the  odd  number  of  toes  (Perisso- 
dactyla)  or  even  number  (Artiodactyla).  In  the  Perisso- 
dactyles  there  may  be  three  toes  on  each  foot,  as  in  the  rhi- 
noceros, or  one,  as  in  the  horse  ;  while  in  the  Artiodactyles 
there  may  be  four  toes  (Hippopotamus),  or  two,  as  in  the 
giraffe,  or  two  functional  and  two  rudimental,  as  in  the  ox 
and  deer,  i.  e.,  most  Ruminants.  The  more  generalized  ex- 
isting form  of  Ungulates  is  the  tapir ;  the  most  specialized 


ORDER  OF   UNGULATES.  601 

type  is  the  horse,  with  its  single  toe  on  each  limb.  A  large 
number  of  extinct  Tertiary  Ungulates  in  the  Western  States 
and  Territories,  and  the  Tertiary  basins  of  Paris  and  Lon- 
don, more  or  less  allied  to  the  tapir,  especially  Coryphodon, 
Anoplotherium,  Palceotherium,  etc.,  were  generalized  or 
ancestral  forms,  from  which  the  modern,  more  specialized 
types  have  probably  been  evolved,  and  a  study  of  these  fossil 
Ungulates  shows  that  there  was  then  (i.  e.9  in  Eocene  times) 
an  essential  unity  of  organization  in  all  Ungulates,  including 
the  Ruminants  ;  the  breaking  up  of  the  Ungulate  stem  into 
special  groups,  along  favored  lines  or  paths  of  development, 
having  resulted  in  a  gradual  improvement  and  .elabora- 
tion of  particular  parts,  which  rendered  them  more  fitted 
for  their  present  life,  and  more  intelligent  in  meeting  and 
overcoming  the  emergencies  their  more  complex  surround- 
ings subjected  them  to.  Thus  in  the  Eocene  Ungulates, 
such  as  Coryphodon,  the  cerebrum  was  small,  without  convo- 
lutions, indicating  a  slight  degree  of  intelligence  compared 
with  the  modern  Ungulates,  while  the  gradual  differentiation 
of  the  horse,  with  its  single  toe  and  hoof,  from  its  tapir-like 
ancestors,  is  a  marked  example  of  the  intelligent,  beneficent 
selection  of  favored,  useful  types  which  has  gone  on  from  the 
earliest  geological  times. 

All  this  specialization  of  type  involved  the  destruction  of 
great  numbers  of  forms  unfitted  to  withstand  changes  in 
their  surroundings,  or  not  sufficiently  intelligent  or  wary  to 
avoid  the  attacks  of  carnivorous  forms,  and  thus  the  present 
number  of  Ungulates  is  much  exceeded  by  the  fossil  forms. 

Perissodactyles.  The  odd-toed  Ungulates,  on  the  whole, 
stand  lower  than  the  even-toed  forms.  They  all  have  at 
least  twenty-two  dorsal  and  lumbar  vertebrae,  and  a  simple 
stomach,  with  a  large,  sacculated  coecum.  The  tapirs  are 
the  more  elemental,  generalized'  forms.  Fossil  tapirs  occur 
in  the  older  Tertiary  beds  of  the  West.  The  snout  is 
almost  proboscis-like,  and  the  legs  are  moderately  long,  with 
four  toes  in  front,  three  toes  behind.  The  tapirs  inhabit  the 
tropics  of  the  New  World  and  Sumatra.  They  are  succeeded 
by  the  rhinoceros,  represented  in  this  country  by  a  number 
of  extinct  Tertiary  allies,  the  living  species  being  restricted 


602  ZOOLOGY. 

to  Africa  and  the  East  Indies.  The  skin  is  remarkably  thick 
and  dense,  while  these  animals  have  either  one  or  two  long 
median  horns  growing  from  the  skin  of  the  nose.  A  rhinoc- 
eros contemporary  with  early  European  man  formerly  inhab- 
ited England,  France,  and  Germany,  and  extended  into  Si- 
beria. 

A  number  of  fossil  forms  lead  up  to  the  family  compris- 
ing the  horse,  ass,  zebra,  and  quagga,  etc.,  in  which  there 
is  a  single  toe,  being  the  third  on  each  limb.  Their  den- 
tion  is  — 

6      1-1       4-43-3 


The  genealogy  or  series  of  ancestral  extinct  Ungulates 
leading  from  tapir-like  forms  to  the  modern  horse  has  been 
worked  out  partly  by  Huxley,  and  especially  by  Marsh,  who 
has  with  Leidy  discovered  a  large  series  of  remains  in  the  Ter- 
tiary beds  of  central  and  western  United  States,  America  being 
the  original  home  of  the  horse.  The  earliest  member  of  the 
series  directly  leading  up  to  the  horse  was  Eohippus,  an  older 
eocene  form,  about  as  large  as  a  fox,  which  had  four  well- 
developed  toes  and  the  rudiments  of  a  fifth  on  each  fore-foot, 
and  three  toes  behind.  In  later  eocene  beds  appeared  an 
animal  (  Orohippus)  of  similar  size,  but  with  only  four  toes  in 
front  and  three  behind.  In  newer  beds,  i.  e.,  lower  miocene, 
are  found  the  remains  of  Mesohippus,  which  was  as  large  as 
a  sheep  and  had  three  toes  and  the  splint  of  another  in  each 
fore-foot,  with  but  three  toes  behind.  In  later  miocene  beds 
another  form  (AncliitJierium  or  MioJilppus)  had  the  same 
number  of  toes,  but  with  the  "  splint  bone  of  the  outer  or  fifth 
digit  reduced  to  a  short  remnant."  The  splint  bones,  then, 
represent  two  of  the  digits  of  several-toed  animals.  The  suc- 
ceeding forms  were  still  more  horse-like.  "  In  the  Pliocene 
above,  a  three-toed  horse  (Hipparion  or  ProtoMppus),  about 
as  large  as  a  donkey,  was  abundant,  and  still  higher  up  a  near 
ally  of  the  modern  horse,  with  only  a  single  toe  on  each  foot 
(Pliohippus)  makes  his  appearance.  A  true  Equus,  as  large 
as  the  existing  horse,  appears  just  above  this  horizon,  and 
the  series  is  complete."  (Marsh.)  Fossil  horses  extended 
over  portions  of  North  and  South  America,  but  became  ex- 
tinct before  the  present  Indians  appeared. 


THE  HOESE  AND  ITS   VARIETIES. 


603 


The  horse  (Equus  cdballus  Linn.)  is  the  most  useful  of  all 
domestic  animals,  and  next  to  ships  a  prime  means  of  the 
diffusion  of  civilization.  By  artificial  selection  a  great  num- 


ber of  varieties,  races,  and  strains  have  been  produced, 
adapted  for  the  performance  of  different  kinds  of  work.  The 
horse  only  exists  in  a  domesticated  state.  Sanson  states  thr.t 


604  ZOOLOGY. 

the  horse  in  the  Orient  has  five,  and  in  the  west  (Africa)  six 
lumbar  vertebrae  ;  in  Arabia  both  forms  occur  ;  in  the  horse 
with  but  five  lumbar  vertebrae  the  shape  of  the  skull  is  also 
different.  The  Hemippus,  the  tarpau  and  muzir  of  Tartary, 
as  well  as  the  white,  shaggy  horse  of  the  elevated  plains  of 
Pamir  in  central  Asia  which  is  often  regarded  as  the  original 
stock,  may  be  a  race  which  has  returned  to  a  wild  state,  since 
partly  wild  horses  occur  in  Syria,  on  the  Don,  and  live 
in  great  herds  on  the  llanos  and  pampas  of  South  America. 
There  are  two  primitive  races  of  horses,  the  Oriental  and 
Western.  To  the  first  belong  three  types  :  the  Arabian,  with 


the  Berber,  Andalusian,  Neapolitan ;  and  in  England  the 
blood  horse ;  the  Nizaischan  type  of  the  Deccan,  India,  to 
which  belong  the  Persian,  Turkestan,  Turkish  horses,  and 
the  Tartarian.  The  western  races  comprise  the  Frieseland, 
to  which  belong  the  Brabant,  Holstein,  Mecklenburg,  and 
the  English  farm-horse,  and  among  others  the  Percheron 
horse,  of  France.  Ponies  are  dwarf  horses  produced  in  cool, 
mountanous  areas,  such  as  the  Shetland  Islands.  The  wild 
ass  (Equus  onager  Brisson)  ranges  from  the  Indus  to  Meso- 
potamia. Equus  hemionus  Pallas,  the  Dschiggetai  or  Kiang, 
in  herds  in  central  Asia  and  Mongolia.  The  hinny  and 


EVEN-TOED    UNGULATES.  605 

mule  are  infertile   hybrids  of  the  horse   and  ass    (Equus 
asinus  Linn.). 

Artiodactyles. — The  even-toed  Ungulates  comprise  the 
peccary,  pig,  hippopotamus,  and  the  Euminants  represented 
by  the  deer,  sheep,  ox,  and  camel.  The  pig  and  peccary  are  the 
descendants  of  a  number  of  extinct  earlier  forms  which  flour- 
ished in  the  Tertiary  Period ;  the  pig,  as  Marsh  observes, 
having  held  its  own  with  characteristic  pertinacity.  The 
Hippopotamus  (Fig.  522)  has  a  large  head,  with  large  canines, 
a  clumsy  body,  and  short,  three-toed  legs.  Hippopotamus 
amphibius  Linn.,  ranges  from  the  Upper  Nile  to  the  Cape  of 
Good  Hope,  and  westward  to  Senegambia.  It  is  nearly 
•3J  metres  (11  feet)  in  length. 

Ruminantia. — The  remaining  Artiodactyles  are  called 
Ruminants,  from  the  fact  that  they  chew  their  cud.  The 
molars  are  provided  with  two  double  crescent-shaped  folds 
(compare  Fig.  490).  The  stomach  (Fig.  523)  is  divided  into 
at  least  three,  usually  four  compartments,  i.e.,  the  paunch, 
the  reticulum  or  honeycomb,  so  named  from  the  polygonal 
cells  on  its  interior,  the  psalterium  or  manyplies,  and  lastly 
the  rennet  or  true  stomach.  When  a  sheep,  cow,  or  any 
other  Ruminant  feeds,  it  thrusts  out  its  long  tongue,  seizes 
a  bunch  of  grass,  and  bites  it  off  by  pressing  the  incisors 
of  the  lower  jaw  against  the  toothless  gum  of  the  opposing 
part  of  the  upper  jaw  ;  the  mouthful  of  grass  is  then  swal- 
lowed, mixed  with  much  saliva.  When  its  appetite  is  satis- 
fied it  seeks  a  retired  spot  away,  from  its  carnivorous  ene- 
mies, if  not  a  domesticated  animal,  and  after  lying  down, 
suddenly  regurgitates  a  ball  of  grass,  the  cud,*  which  it  slow- 
ly grinds  up  between  its  molar  teeth  into  a  pulp.  The 
cropped  grass  passes  into  the  honeycomb  and  paunch ;  the 
manyplies  serves  as  a  strainer  for  the  pulp,  which  in  the 
fourth  stomach  is  digested  by  the  gastric  juice. 

Among  a  number  of  fossil  forms  leading  up  to  the  exist- 

*  The  regurgitation  of  the  cud  is  probably  due  to  a  sudden  and  sim- 
ultaneous contraction  of  the  diaphragm  and  of  the  abdominal  muscles, 
which  compresses  the  contents  of  the  rumen  and  reticulum,  and 
drives  the  sodden  fodder  against  the  cardiac  aperture  of  the  stomach, 
which  opens  and  the  cud  is  propelled  into  the  mouth.  (Huxley.) 


006 


ZOOLOGY. 


EVEN-TOED    UNGULATES. 


Fig.  525.-Skeleton  of  Sivatherium  restored.-Af  ter  Hawking, 


Fig.  52Q.-Virginian  Deer.-From  Caton. 


008 


ZOOLOGY. 


ing  deer  and  antelopes  is  the  Sivatherium  (Fig.  524,  525) 
of  the  Tertiary  beds  of  the  Himalaya  Mountains,  which  had 
two  pairs  of  horns,  and  were  gigantic  creatures,  nearly  as 


--^rripGC  — .  __ 

Fig.  527.— Elk  or  Wapati.— Prom  Caton's  Antelope  and  Deer  of  America. 

bulky  as  an  elephant,  and  of  the  singular  form  approxi- 
mately indicated  by  the  accompanying  illustrations,  having 
affinities  to  the  antelopes  and  the  giraffe. 

The  deer  family  (Cervidce)  is  represented  in  the  United 


THE  SHEEP  AND  ITS  VARIETIES. 


609 


States  by  the  common  Virginian  deer  (Cariacus  Virginianus 
Gray,  Fig.  526),  the  elk  or  wapiti  (Cervus  Canadensis  Erxle- 
ben,  Fig.  527),  and  the  caribou  (Rangifer  caribou  Audubon 
and  Bachman),  which  is  probably  a  variety  of  the  European 
reindeer  (R.  tarandus  Sundevall).  In  these  beautiful,  grace- 
ful forms  the  solid  antlers  are  cast  off  annually  ;  with  the 
exception  of  the  reindeer  the  females  or  does  have  no  antlers. 
The  prong-horn  antelope  (Antilocapra  Americana  Ord, 


Fig.  528.— Head  of  young  Prong-horn  Antelope.— After  Hays. 

Fig.  528)  so  characteristic  of  the  western  plains,  also  drops 
its  horns  in  the  autumn,  though  they  are  hollow  when  shed 
and  with  a  persistent  core  as  in  the  ox  and  goat.  It  crops 
grass,  not,  like  the  deer,  eating  leaves  of  trees  and  shrubs  ; 
"in  fleetness  it  excels  all  other  quadrupeds  of  our  conti- 
nent," though  it  is  short  winded,  and  does  not  run  a  great 
distance  (Caton).  In  its  horns,  hollow  when  cast  off,  and  the 
-all  bladder,  which  is  absent  in  the  Cervida*,  the  prong-horn 


010 


ZOOLOGY. 


connects  the  deer  family  with  the  Bovidce,  represented  by 
the  sheep,  goat,  antelope,  gazelle,  and  ox. 

The  domestic  sheep  (Ovies  aries  Linn.)  is  not  a  natural 
species,  but  an  association  of  races  whose  specific  origin  is 
obscure.  Some  authors  regard  the  turf  sheep  of  the  stone 
age  of  Europe  as  the  ancestor  of  the  domestic  sheep,  as  forms 
like  it  are  now  living  in  the  Shetland  Isles  and  in  Wales. 
It  was  of  small  size,  with  slender  limbs,  and  erect,  short 
horns.  This  sheep  was  supplanted  by  a  curved,  large-horned 
form,  the  modern  domestic  sheep.  This  latter  form  is  pos- 
sibly the  descendant  of  the  Ovis  argali  Pallas,  of  Asia,  which 
in  North  America  is  represented  by  the  Ovis  montana  Cuvier, 
the  Rocky  Mountain  sheep  or  big-horn  (Fig.  530),  still  com- 
mon on  the  less  accessible  summits  along  the  upper  Missouri 
and  Yellowstone  Rivers,  as  well  as  the  mountains  of  Wy- 
oming and  Montana. 
In  the  same,  though 
higher  and  more  inac- 
cessible situations  lives 
the  rare  mountain 
goat,  Aploceros  monta- 
nus  Richardson,  whose 
horns  are  jet  black  and 
polished,  slender  and 
conical,  like  those  of 
the  Swiss  chamois.  It 
is  found  sparingly  in 
the  higher  summits  of 


Fig.  529.— Horns  at  different  ages  of  the  Prong- 
horn  Antelope,  showing  the  hollow  structure  of 
the  horn  when  ghed.—  After  Hays. 


the  Rocky  Mountains 
and  the  Cascade  range  ; 
an  individual  has  within  a  few  years  been  shot  on  Mount 
Shasta,  California.  Passing  by  the  gazelles  and  true  an- 
telopes we  come  to  another  characteristic  American  an- 
imal, the  musk  sheep  (Ovibos  moscliatus  Blainville, 
Fig.  531),  now  confined  to  the  arctic  regions.  A  closely 
allied  species,  Ovibos  prisons  of  Rutimeyer,  formerly  during 
the  post-glacial  period  existed  in  England,  France,  and  Ger- 
many. Closely  allied  to  the  musk  sheep  is  a  fossil  form 
(Bootherium  of  Leidy)  which  is  regarded  by  Rtitimeyer  and 


THE  BISON. 


611 


others  as  a  musk  sheep  (Ovibos prisons  Eiltimeyer).  If  this 
is  the  case  the  musk  sheep,  or  a  species  closely  allied  to  it, 
formerly  extended  to  the  Middle  States  at  or  near  the  close 
of  the  glacial  period. 

We  now  come  to  the  bison  and  ox.     The  American  bison 


Fig.  530.— Rocky  Mountain  Sheep  or  Big-Horn.—  From  Brehm's  Thierleben. 

(Bison  Americanus  Gmelin)  formerly  ranged  from  Virginia 
and  Lake  Champlain  to  Florida,  and  westward  from  the 
northern  limit  of  trees  to  the  Rocky  Mountains  and  eastern 
Mexico.  It  is  now  in  danger  of  extermination,  being  mainly 
restricted  to  a  few  herds  on  the  plains.  It  is  closely 


012  XOOLOQT. 

allied  to  the  European  bison,  (Bison  Europceus  Owen),  the 
"auroch,"  now  preserved  in  the  forests  of  Bialowicza,  and 
living  wild  in  Caucasus.  Bos  primigenius  Bojanus,  which 


in  the  time  of  Caesar  lived  in  Germany  and  England  bear- 
ing the  name  "urus,"  is  the  "ur"  of  the  Niebelungen 
song.  From  it  has  descended  the  half-wild  cattle  in  certain 


THE  OX  AND  ITS   VARIETIES. 


613 


English  parks,  also  certain  large  domestic  races,  such  as  the 
Holstein  and  Friesland  breeds.  From  another  fossil  species 
(Bos  longifrons  Owen)  arose  the  so-called  brown  cattle  of 
Switzerland,  and  the  "runts"  of  the  Scottish  Highlands. 
Still  other  domestic  races  are  traced  back  to  another  fossil 


s 


uaternary  species,  Bos  frontosus  Nilsson.  Our  present 
races  of  domestic  cattle,  however,  do  not  represent  a  genuine 
species,  but  a  number  of  races  which  have  descended  from 
several  fossil  species  ;  the  name  Bos  taurus  (Fig.  532)  is 
simply,  then,  a  conventional  name  (Cams'  Zoologie).  The 
bison  is  known  to  breed  with  cattle  in  the  Western  States, 


,;U  ZOOLOGY. 

though  whether  the  hybrids  thus  produced  are  fertile  or  not 
is  unknown. 

The  ox  is  succeeded  by  the  giraffe,  with  its  long  neck, 
which  makes  it  the  tallest  of  all  quadrupeds. 

The  last  family  of  Ungulates,  the  Camelida},  comprises  the 
camels  of  the  Old  World,  and  the  llama  and  vicuna  of  South 
America.  In  former  (Tertiary)  times  a  llama-like  animal 
inhabited  the  Pacific  coast  to  Oregon.  In  the  camels  the 
upper  lateral  incisors  are  present;  the  stomach  is  less 
distinctly  divided  into  four  chambers,  the  third  stomach,  as 
such,  is  wanting,  though  the  second  stomach  has  the  deep 
cells,  which  suggested  the  fable  that  the  camel  stores  up  a 
supply  of  water  in  its  stomach  for  its  march  over  deserts. 


Fig.  533.— Skull  of  Lion. 

The  toes  have  very  large,  thick  pads,  while  the  hoofs  are 
reduced  to  nail-like  proportions. 

Order  11.  Carnivora  (Ferae}. — The  bear,  cat,  tiger,  and 
lion  recall  the  leading  forms  of  this  order.  The  skull  is 
massive,  though  the  head  is  small  or  of  moderate  size  ;  the 
teeth  are  all  well  developed,  especially  the  canines  ;  the  mo- 
lars usually  have  two  or  three  roots,  and  the  feet  have  large 
claws.  The  stomach  is  simple.  The  cerebral  hemispheres 
of  the  lower  carnivores  have  usually  but  three  distinct  con- 
volutions, while  the  latter  are  much  more  numerous  and 
complicated,  the  brain  itself  being  broader,  in  the  aquatic 
forms  (Pinnipedia).  The  group  is  divided  into  two  sub- 
orders, i.e.  the  Pinnipedia  or  seals,  and  the  land  species  (Fis- 
sipedia).  In  the  former  group  the  feet  are  webbed,  the  toes 


BEARS  AND   THEIR  ALLIES. 


615 


being  connected  ;  the  wrist  and  foot  only  projecting  beyond 
the  skin  of  the  body,  and  there  are  no  external  ears,  or  only 
small  ones. 

The  walrus  (Fig.  534),  the  seals,  and  the  eared  seals  or 
sea-lions  ( OtariidcB) 
are  the  types  of  the 
aquatic  Carnivores ; 
the  sea-lions  can  walk 
on  all  fours,  and  in 
certain  peculiarities  of 
the  skull  they  resem- 
ble the  bears. 

Of  the  terrestrial, 
normal  Carnivora,  the 
raccoon,  coati,  Cerco- 
leptes,  and  bear,  to- 
gether with  a  number 
of  extinct  forms,  are 
the  more  generalized 
or  lower  types.  They 
are  plantigrade,  and 
while  standing  at  the 
base  of  the  carnivorous 
series,  have  some  fea- 
tures suggesting  and 
anticipating  those  of 
the  lemurs,  and  mon- 
keys. The  raccoon, 
Procyon  lotor  (Linn.), 
abounds  throughout 
the  United  States.  Al- 
lied to  it  is  the  coati 
(Nasud)  of  Central 
America,  a  creature 
about  the  size  of,  and 
with  the  general  hab- 
its of  the  raccoon,  being  an  exceedingly  knowing  and  mis- 
chievous animal.  A  number  of  extinct  Eocene  mammals 
are  also  allied  to  a  small  plantigrade,  long -tailed  carnivore, 
Cercoleptes,  which  resembles  the  Primates  in  its  two  cutting 


616 


ZOOLOGY. 


pre-molars  and  three  true  molars ;  while  the  rami  of  the 
mandible  are  coossified ;  for  these  reasons  it  was  placed 
by  F.  Cuvier  between  the  orders  Carnivora  and  Primates 
(Cope).  It  is  allied  to  the  raccoon,  is  called  the  kincajou, 
and  lives  in  northern  South  America. 

The  bears  have  a  thick,  clumsy  body,  with  a  rudimentary 
tail,  and  the  teeth  are  broad  and  tuberculated,  so  that  they 
can  live  indifferently  on  fish,  insects,  or  berries.  Our  North 
American  species  are  the  polar  bear  (Ursus  maritimus 
Linn.)  and  Ursus  arctos  Linn.,  with  its  varieties  of  brown, 


Fig.  535.— Skeleton  of  the  Polar  Bear,  showing  the  plantigrade  feet.  51,  scapula  ; 
53,  hnmerus;  54,  radius;  55,  ulna;  62,  ilium;  63,  ischium;  65,  femur;  66,  tibia;  67, 
fibula  ;  cl,  calcareum  ;  C,  cervical  vertebrae. — After  Owen. 

cinnamon  and  grizzly  bears  ;  and  the  true  black  bear,  Ursus 
Americanus  Pallas. 

The  bears  are  succeeded  by  the  Mustelidce,  or  the  otter, 
skunk,  badger,  wolverene,  weasel,  mink,  ermine,  etc.,  nearly 
all  of  which  ^are  valuable  for  their  furs. 

The  dog  family  (Canidce)  is  represented  by  the  fox,  wolf, 
and  dog.  The  gray  fox  ( Urocyon  Virginianus  Erxleben)  the 
common  red  fox  (  Vulpes  vulgaris  Fleming),  with  its  varie- 
ties, the  cross,  silver,  and  black  fox,  as  well  as  the  wolf 
(Canis  lupus  Linn.),  are  valuable  for  their  furs.  The  wolf 
is  mostly  gray  northward,  becoming  "southward  more  and 


] 


THE  SPECIES  OF  DOGS  AND  CATS.  617 

more  blackish  and  reddish,  till  in  Florida  black  wolves  pre- 
dominate, and  in  Texas  red  ones."  (Jordan's  Manual  of 
Vertebrates.)  The  prairie  wolf  or  coyote  (Canis  latrans 
Say),  is  characteristic  of  the  Western  plains  and  Pacific  coast. 
The  Indian  dogs  breed  with  the  coyote,  and  the  offspring  is 
fertile.  (Coues. )  This  fact  appears  to  support  the  theory 
that  the  domestic  dog  (with  its  conventional  name  Canis 
familiaris  Linn.)  is  a  descendant  of  the  wolf.  On  the  other 
hand,  Fitzinger  in  his  "Researches  on  the  Origin  of  the 
Dog,"  states  that  fourteen  kinds  of  dogs  can  be  distinguished 
in  the  Roman  and  Greek  records  ;  of  these  he  considers  five 
to  be  principal  types  or  species,  five  others  climatic  varieties, 
the  remainder  being  either  breeds  artificially  produced  or 
hybrids.  As  regards  the  Egyptian  dogs,  seven  kinds  may  be 
distinguished,  besides  the  jackall,  three  of  them  being  dis- 
tinct species.  He  believes  that  wolves,  jackalls,  foxes,  etc., 
are  species  quite  distinct  from  the  domestic  dog  ;  they 
may  have  interbred  with  the  latter,  and  thus  influenced  cer- 
tain breeds  ;  but  they  are  not  the  parents  of  the  domestic 
dog.  He  concludes  that  there  are  seven  species  among  our 
dogs : — C.  domesticus,  extrarius  or  spaniel  and  Newfound- 
land dogs,  vertagus  or  badger  dog,  sagax  or  hound,  tnolossus 
or  bulldog,  Icporarius  or  greyhound,  and  the  naked  dog, 
C.  caribaus.  Among  half-wild  dogs  is  the  dingo  or  hunt- 
ing-dog of  Australia,  which  goes  in  packs. 

The  Viverra  and  Genetta  or  civet  cats,  and  the  hyaenas 
lead  to  the  cat  family,  which  stands  at  the  head  of  the  Oar- 
nivora.  The  panther,  leopard,  tiger,  and  lion  belong  to  the 
genus  Felis.  The  Felis  concolor  Linn.,  cougar  or  puma, 
ranges  over  both  continents;  it  is  1-1-3  metres  in  length. 
The  domestic  cat,  Felis  domestica  Linn.,  was  first  domes- 
ticated in  Egypt,  the  Greeks  and  Romans  not  possessing 
it ;  the  cat  and  common  marten  were  in  use  as  domesticated 
animals  side  by  side ;  and  at  the  same  time  in  Italy,  nine 
hundred  years  before  the  crusades.  It  appears  that  the  do- 
mestic cat  of  the  ancients  was  Mnstela  foina  (Rolleston). 

Of  the  lynxes  there  are  two  species  in  North  America, 
Lynx  rufus  Rafinesque,  the  American  wildcat,  and  the 
Canada  lynx,  Lynx  Canadensis  Rafinesque,  the  latter  being 
much  the  larger  species. 


618  ZOOLOGY. 

Order  XII.  Primates. — The  last  and  highest  order  of 
mammals  contains  a  series  beginning  with  creatures  resem- 
bling squirrels  and  bats,  i.  e.,  the  lemurs,  and  comprising 
monkeys,  apes,  and  ending  with  man.  In  all  the  Primates, 
the  legs  are  exserted  almost  or  quite  free  from  the  trunk, 
with  the  great  toe  of  the  hind  foot  usually  enlarged  and  op- 
posable  to  the  others  ;  nails,  except  in  the  marmosets,  replace 
claws  ;  the  teeth  are  usually  of  the  following  formula  : 

2-2      1-1       3-3       3-3 
1 2=2'  C1^T  ^£=8*  ^3-3' 

with  one  exception  canine  teeth  are  always  present ;  the  pre- 

2 2  Q 3 

molars  are  usually  g— 9,  but  in  the  American  monkeys  =--5. 

The  hemispheres  of  the  brain  may  in  the  lower  forms  be 
quite  smooth,  but  in  all  there  is  a  well-developed  "  calcarine 
furrow,"  giving  rise  to  a  "hippocampus  minor"  within  the 
posterior  cornu  of  the  ventricle,  by  which  the  posterior  lobe 
of  the  cerebrum  is  traversed  (Flower).  The  collar-bones 
(clavicles)  are  for  the  first  time  in  the  series  well  developed. 
The  placenta  is  also  different  in  shape  from  that  of  other 
mammals,  being  round,  disk  or  cake-like. 

The  Primates  are  divided  into  two  sub-orders,  i.  e.,  the 
Prosimice  and  Anthropoidea.  The  former  group  embraces 
the  lemurs,  which  vary  in  size  from  that  of  a  rabbit  to  a 
large  monkey.  They  are  covered,  the  face  as  well  as  the  rest 
of  the  body,  with  a  dense  fur ;  walk  on  all-fours,  usually 
have  long  tails,  though  the  lori  is  tailless,  while  the  fore 
limbs  are  shorter  than  the  hind  limbs.  The  skull  is  small, 
flattened,  and  narrow  in  front ;  the  brain-cavity  small  in 
proportion  to  the  rest  of  the  skull,  i.  e.,  the  face  compared 
with  the  monkeys.  The  cerebral  hemispheres  are  small  and 
flattened,  the  frontal  lobes  narrow  and  pointed,  and  behind 
they  only  slightly  cover  the  cerebellum. 

By  some  authors  the  lemurs  are  separated  from  the  Pri- 
mates, the  Insectivora  and  Cheiroptera  being  placed  between 
the  Prosimice  and  the  other  Primates.  They  have  characters 
in  which  they  resemble  Insectivora,  Rodentia,  and  Carnivora, 
but  the  weight  of  organization,  or  the  sum  of  their  charac- 
ters, ally  them  nearest  to  the  monkeys.  They  are  therefore 
essentially  a  generalized  or  ancestral  type.  Recent  discov- 


THE  PRIMATES.  619 

eries  have  led  to  the  hypothesis,  that  from  still  older,  more 
generalized  types,  four  lines  of  development,  respectively 
culminating  in  the  typical  Carnivores,  Cetaceans,  lemurs,  and 
monkeys,  have  taken  their  origin.  That  the  lemurs,  though 
now  restricted  to  Madagascar,  eastern  Asia,  and  South 
Africa,  were  preceded  by  still  more  generalized  types  on  the 
American  Continent,  is  indicated  by  the  discovery  of  fossil 
bones  in  the  Eocene  beds  of  the  Rocky  Mountains,  referred 
by  Marsh  and  Cope  to  the  Primates ;  Marsh  stating  that 
the  principal  parts  of  the  skeleton  are  "  much  as  in  some  of 
the  lemurs." 

Allied  to  the  true  lemurs  is  a  very  puzzling  creature,  the 
aye-aye  or  Chiromys,  of  Madagascar,  whose  dentition  differs 
from  that  of  all  other  Primates,  and  resembles  that  of  the 
Rodents  ;  the  thumb  also  is  not  truly  opposable,  and  all  the 
hind  digits,  except  the  great  toes,  have  claw-like  nails.  The 
Galago,  of  West  Africa,  somewhat  recalls  the  Insectivora, 
while  "  in  the  more  active  and  flexible-bodied  Lemuridce, 
the  trunk-vertebrae  resemble  in  proportions,  connections,  and 
direction  of  neural  spines  those  of  the  agile  Carnivora." 
(Owen.) 

The  genuine  Primates  or  suborder  AntJiropoidea  are,  in 
brief,  characterized  by  the  large,  convoluted  cerebral  hemi- 
spheres which  nearly,  or  in  the  higher  apes  and  man,  conceal 
the  cerebrum  when  seen  from  above.  *  The  ears  are  rounded, 
with  a  distinct  lobule,  and  the  two  mammae  are  pectoral. 
These  AntJiropoidea  are  divided  into  two  subdivisions,  the 
first  comprising  the  monkeys  and  apes,  and  the  second,  man. 
In  the  first  group  (Simice),  the  body  is  prone,  the  animal 
walking  on  all-fours,  only  the  orang  and  gorilla  walking 
partly  erect ;  the  great  toe  is  rather  short,  thumb-like,  and 
opposable  to  the  fingers,  while  the  body  is  very  hairy.  The 
monkeys  of  the  New  World  have  a  wide  septum  to  the  nose, 
and  are  hence  called  Platyrhinw  ;  they  also  have  long  tails. 

The  little,  squirrel-like,  gregarious  marmosets  are  the  small- 
est of  the  monkeys  and  nearest  allied  to  the  lemurs.  They 
walk  on  all -fours,  the  anterior  extremities  being  like  the 


*In  the  low  Hapcde  and  Cebus,  however,  the  cerebrum  projects 
backward  as  far  or  even  farther  than  in  man  (Gill). 


620  ZOOLOGY. 

hind  feet,  and  resting  on  the  same  plane,  serving  as  a  paw  ; 
the  teeth  are  sharply  tubercled,  and  the  nails,  except  those  of 
the  great  toe,  are  claw-like.  The  cerebral  hemispheres  are 
nearly  smooth,  though  relatively  large.  Jacclms  and  Midas 
are  the  typical  genera,  inhabiting  South  America.  While 
the  marmosets  (MididcB)  have  but  thirty-two  teeth,  in  the 
true  platyrrhine  monkeys  there  are  thirty-six  teeth ;  there 
being  an  additional  molar  on  each  side  of  each  jaw,  and  the 
thumb  is  slightly  opposable  to  the  fingers  (though  a  true 
thumb  is  wanting  in  the  spider  monkeys).  The  New  World 
monkeys  also  have  long  prehensile  tails,  so  useful  in  climb- 
ing as  to  be  sometimes  called  a  fifth  hand,  as  seen  in  the 
spider  monkeys  (Ateles),  in  which  the  tail  underneath  is 
naked  and  very  sensitive.  The  skull  varies  greatly  in  the  dif- 
ferent genera,  as  does  the  brain,  which  in  Chrysotlirix,  etc., 
is  nearly  smooth,  while  in  Cebus  the  hemispheres  are  nearly 
as  much  convoluted  as  in  the  catarrhine  apes.  (Huxley.) 

The  monkeys  of  the  Old  World  intergrade  with  the  apes, 
and  are  thus  more  specialized  or  highly  developed  than 
those  of  the  New  World.  The  septum  of  the  nose  is  narrow, 
hence  they  are  said  to  be  catarrhine  or  thin-nosed,  while  the 
tail  is  short  and  not  prehensile. 

The  catarrhine  monkeys  (Cercopithecida)  walk  on  all- 
fours  ;  the  body  being  horizontal  or  prone  ;  they  have  thirty- 
two  teeth,  as  in  man,  though  the  canines  are  large  and 
sharp ;  the  thumb  is  well  developed,  and  they  are  truly 
quadrumanous ;  the  skull  has  a  comparatively  large  facial 
angle,  and  the  hemispheres  of  the  brain  are  well  furrowed. 
They  have  highly-colored,  naked  callosities  over  the  ischiatic 
bones,  and  cheek-pouches  for  the  temporary  reception  of 
the  food.  Of  the  baboons,  with  their  dog-like  muzzles  and 
short  tails,  the  mandrills  are  the  most  noticeable,  with  their 
white  beards,  scarlet  lips,  and  blue  cheeks  ;  they  are  less 
arboreal  than  the  macaques  of  Asia,  running  about  .over 
rocks  on  all-fours.  The  common  monkeys  of  menageries 
are  the  macaques  (Macacus)  of  India.  All  the  foregoing 
catarrhine  monkeys  have  a  simple  stomach,  as  in  man,  but 
in  the  sacred  monkey  of  India  (Semnopithecus)  and  the 
African  thumbless  Colobus,  the  stomach  is  more  complex, 
and  there  are  no  cheek  pouches. 


THE  MONKEYS  AND  APES.  621 

The  apes  live  in  trees,  only  occasionally  walking  on  the 
ground ;  their  posture  is  semi-erect ;  they  are  tailless,  the 
fore  legs  are  much  longer  than  the  hind  legs,  and  used  as 
arms,  the  radius  being  ca- 
pable of  complete  prona- 
tion  and  supination.  In 
the  form  of  the  skull,  of 
the  brain  with  its  convolu- 
tions, and  in  the  teeth, 
there  is  a  still  nearer  ap- 
proach to  man. 

There  are  three  typical 
forms  or  genera  of  apes, 
i.e.,  the  gibbon  (Hylobates, 
Fig.  536)  ;  the  orang  (Mi- 
metes  pithecus)  and  chim- 
panzee (M.  niyer,  Fig. 
537),  and  the  gorilla.  The 
gibbons  are  nearest  to  the 
monkeys ;  they  are  little 
less  than  a  metre  (3  feet) 
in  height,  and  are  very 
slender,  with  very  long 
arms,  so  that  they  are  rapid, 
agile  climbers,  also  run- 
ning over  the  ground  with 
ease  and  rapidity ;  when 
standing  erect  the  fingers 
touch  the  ground ;  only 
the  thumbs  and  great  toes 
have  true  nails,  in  all  the 
higher  apes  the  nails  of  all 
the  digits  being  flattened  ; 
the  spinal  column  is  nearly 
straight ;  they  have  four- 
teen pairs  Of  ribs  and  Fig-  53f>.-Skeleton  of  Siamang  Ape,  a  gib- 
.  J  bon. — After  Owen. 

eighteen  dorso-lumbar  ver- 
tebrae, there  being  in  the  other  apes  usually  seventeen,  as  in 
man.     The  siamang  lives  in  the  forest  of  Sumatra ;  others 
inhabit  Java,  Borneo,  Cambogia,  etc. 


622 


ZOOLOGY. 


The  orang-outang  is  1-38  metres  (44-5  feet)  high  ;  it  has 
twelve  pairs  of  ribs,  the  same  number  as  in  man  ;  the  arms 
are  very  long,  reaching  the  ground,  so  that  in  walking  they 
rest  on  their  knuckles,  swinging  the  body  through  their  long 
arms  as  if  walking  on  crutches ;  their  posture  is  only  par- 
tially erect.  The  forehead  is  less  strongly  marked  than  in 


Fig.  537.— The  Chimpanzee,  variety  Tshego.— From  Brehin's  Thierleben. 

the  other  apes,  showing  better  the  shape  of  the  skull.  The 
volume  of  the  brain,  both  of  the  orang  and  chimpanzee  is 
about  twenty-six  or  twenty-seven  cubic  inches.  The  follow- 
ing table  will  show,  according  to  Wyman,  the  relative 
capacity  of  the  skull  in  the  different  apes  as  compared  with 
man  : 


CHIMPANZEE  AND   GORILLA.  623 

The  average  capacity  of  the  Caucasian  skull  is  92  cubic  inches. 

Australian      "      75 

"  "  "        Gorilla  "      29   to   near  35 

cubic  inches. 
Chimpanzee    "      26 
"  "  "         Orang  "      25  "   - 

According  to  Wyman,  the  range  of  variation  in  different 
races  of  men,  as  seen  in  seventeen  skulls,  is  from  92  to  75 
cubic  inches  ;  in  the  gorilla  from  34  to  25  cubic  inches,  nine 
skulls  having  been  measured.  There  is  but  a  single  species 
of  orang,  which  is  restricted  to  Sumatra  and  Borneo.  It  is 
said  to  be  very  intelligent,  to  possess  a  voice  so  loud  as  to  be 
heard  one  or  two  miles,  and  to  build  a  nest  to  sleep  in. 

The  chimpanzee  and  gorilla  are  only  found  on  the  west 
coast  of  Africa.  The  chimpanzee  (Mimetes  niger  Geoffroy 
with  its  variety  TscJiego,  Fig.  537)  inhabits  the  coast  from 
Sierra  Leone  to  Congo.  It  is  about  1^  metres  (5  feet)  in 
height.  It  can  stand  or  run  erect,  but  it  usually  leans  for- 
ward, resting  on  its  knuckles  ;  the  arms  span  about  half  as 
much  again  as  the  creature's  height.  Both  the  chimpanzee 
and  gorilla  have  fourteen  pairs  of  ribs.  The  chimpanzee  lives 
on  fruit,  is  an  active  climber,  and  nests  in  trees,  changing  its 
rude  quarters  according  to  circumstances.  ,  Eev.  Dr.  Savage 
states  that  "they  generally  build  not  far  above  the  ground. 
Branches  or  twigs  are  bent,  or  partly  broken,  and  crossed, 
and  the  whole  supported  by  the  body  of  a  limb  or  a  crotch. 
Sometimes  a  nest  will  be  found  near  the  end  of  a  strong 
leafy  branch  twenty  or  thirty  feet  from  the  ground. " 

The  gorilla,  like  the  chimpanzee,  goes  in  bands,  but  the 
company  is  smaller,  and  led  by  a  single  adult  male.  They 
make  similar  nests,  which,  however,  in  the  case  of  both  apes, 
afford  no  shelter,  and  are  only  occupied  at  night.  The 
gorilla  sometimes  reaches  the  height  of  about  1 J  metres  (5J 
feet)  and  weighs  about  200  pounds.  Its  ordinary  attitude  is 
like  that  of  the  chimpanzee  ;  there  is  a  web  between  the  first 
joints  of  all  the  fingers  and  three  of  the  toes,  and  both  hands 
and  feet  are  broader,  while  the  body  is  much  more  robust 
than  in  the  other  apes,  being  very  broad  across  the  shoulders. 
The  span  of  the  arms  is  to  the  height  as  three  to  two,  or  a 
little  over  eight  feet.  The  skull  is  thick,  and  the  strength 


624  ZOOLOGY. 

and  ferocity  of  the  creature  is  evinced  by  the  thick  supra- 
orbital  ridges  and  the  high  sagittal  and  lambdoidal  crests  on 
the  top  of  the  skull ;  the  face  is  wide  and  long,  the  nose 
broad  and  flat,  the  lips  and  chin  prominent.  The  gorilla 
walks  like  the  chimpanzee,  though  it  stoops  less.  It  is  very 
ferocious,  bold,  never  running  when  approached  or  attacked 
by  man.  It  lives  on  a  range  of  mountains  in  the  interior  of 
Guinea,  its  habitat,  so  far  as  known,  extending  from  a  little 
north  of  the  Gaboon  River  to  the  Congo. 

Thus,  to  recapitulate,  while  the  gibbons  are  most  remote 
from  man,  the  orangs  approach  him  nearest  in  the  number 
of  the  ribs,  the  form  of  the  cerebral  hemispheres,  and  other 
less  obvious  characters  ;  the  chimpanzee  is  nearest  related  to 
him  in  the  form  of  the  skull,  the  dentition  and  the  propor- 
tions of  the  arms,  while  the  gorilla  resembles  him  more  in 
the  proportions  of  the  leg  to  the  body,  of  the  foot  to  the 
hand,  in  the  size  of  the  heel,  the  curvature  of  the  spine,  the 
form  of  the  pelvis  and  the  absolute  capacity  of  the  skull 
(Huxley).  Anatomists  have  and  do  differ  as  to  whether  the 
chimpanzee  or  the  gorilla  is  nearest  to  man. 

Whether  man  (Homo  sapiens  Linn.),  when  considered 
simply  as  an  animal,  is  the  representative  of  a  distinct  sub- 
class, order,  suborder  or  family,  is  and  may  never  be  settled  ; 
though  the  tendency  among  zoologists  is  to  leave  him  among 
the  Primates,  where  he  was  placed  by  Linnaeus.  When  we 
consider  the  slight  absolute  anatomical  differences  separating 
man  from  the  apes,  and  take  into  account  the  great  variations 
in  form  between  the  different  genera  of  apes,  and  still  more 
in  the  monkeys,  it  seems  best,  throwing  out,  as  we  have  to 
do  in  a  purely  zoological  classification,  the  intellectual  and 
moral  faculties  of  man,  to  adopt  the  view  that  man  is 
the  representative  of  a  group  of  Primates.*  The  absolute 
differences  of  man  from  the  apes  consist  in  the  greater  num- 
ber and  irregularity  of  the  convolutions  of  the  cerebral  hemi- 

*  Geoffrey  St.  Hilaire  placed  man  in  a  kingdom  by  himself  ;  Owen 
assigned  him  to  a  subclass  ;  by  others  he  is  generally  regarded  as  a 
representative  of  an  order  Bimana,  as  opposed  to  the  order  Quadru- 
mana,  or  monkeys  and  apes;  while  from  recent  comparative  studies 
man  is  considered  as  belonging  either  to  a  separate  suborder  or  a  fam- 
ily. 


DIFFERENCES  OF  MAN  FROM  THE  APES        625 

spheres,  which  are  also  much  larger  compared  with  the  cere- 
bellum, and  completely  cover  the  latter ;  the  entire  brain 
being  at  least  double  the  size  proportionately  of  that  of  the 
gorilla  ;  *  it  is  also  stated  that  two  muscles  exist  in  man 
which  have  not  yet  been  found  in  any  ape,  the  extensor  primi 
internodii  pollicis  and  the  peronmus  tertius,  belonging  to  the 
thumb  and  foot  respectively  (Huxley),  f  There  are  also  points 
in  the  origin  of  certain  muscles  which  are  peculiar  to  man,  but 
Huxley  adds  that  all  the  apparently  distinctive  peculiarities 
of  the  muscles  of  the  apes  are  to  be  met  with,  occasionally, 
as  varieties  in  man.  On  the  other  hand,  the  relative  differ- 
ences of  the  skulls  of  the  gorilla  and  man  are,  as  Huxley 
states,  "immense."  In  man  the  cranial  box  overhangs  the 
orbits ;  in  the  gorilla  the  forehead  is  hollowed  out.  The 
hinder  portion  of  the  brain  is  also  much  more  developed  in 
man  than  in  the  apes,  and  in  the  hinder  part  of  the  hemi- 
spheres the  convolutions  are  more  numerous  than  in  the 
chimpanzee,  this  part  in  monkeys  losing  its  convolutions 
altogether  (Wyman).  Man  stands  erect ;  his  arms  span  a 
distance  equal  to  his  height ;  the  spinal  column  has  four 
curves ;  the  skin  of  the  hands  and  feet  of  man  is  highly 
sensitive,  compared  with  that  of  the  apes.  Finally,  as  Cuvier 
stated,  the  grand  distinctive  zoological  character  separating 
man  from  the  other  animals  is  the  possession  of  the  power  of 
speech. 

Sometimes  in  man  the  coccyx  has  one  or  two  more  joints 
than  the  normal  number,  but  the  apes  have  no  tail ;  though 
the  human  embyro,  like  other  young  animals,  has  a  tail, 

*  "  It  must  not  be  overlooked,  however,  that  there  is  a  very  striking 
difference  in  absolute  mass  and  weight  between  the  lowest  human 
brain  and  that  of  the  highest  ape— a  difference  which  is  all  the  more 
remarkable  when  we  recollect  that  a  full-grown  gorilla  is  probably 
pretty  nearly  twice  as  heavy  as  a  Bosjes  man,  or  as  many  an  European 
woman.  It  may  be  doubted  whether  a  healthy  human  brain  ever 
weighed  less  than  thirty-one  or  two  ounces,  or  that  the  heaviest  gorilla 
brain  has  exceeded  twenty  ounces."  In  another  place  Huxley  states 
that  "  an  average  European  child  of  four  year's  old  has  a  brain  twice 
as  large  as  tbat°of  an  adult  gorilla."— Man's  Place  in  Nature. 

\  Dr.  Chapman  has  found  in  the  arm  of  a  gorilla  a  distinct  extensor 
primi  internodii  pollicis  muscle,  but  no  trace  of  the  flexor  longus  polli- 
cis.—American  Naturalist,  June,  1879,  p.  395. 


626 


ZOOLOGY. 


and,  as  "Wyman  has  observed,  it  is  not  impossible  that  it 
might  sometimes  continue  to  exist  after  birth.  The  black 
and  Australian  races  are  slightly  nearer  the  apes  than  civil- 
ized peoples.  In  apes,  as  in  the  lower  mammals,  the  pelvis 
is  higher  than  wide ;  when  there  is  a  degradation  in  the  hu- 
man pelvis  it  tends  to  become  higher  than  wide,  as  seen  in 
the  pelvis  of  the  Hottentots.  In  civilized  man  the  legs  are 
one  half  the  height  of  the  body,  but  in  the  South  African, 
Hottentot,  and  Bushmen  the  legs  are  a  little  less  than  half 
the  height,  and  the  thigh  bone  is  flattened  from  side  to  side, 
as  in  the  gorilla.  The  waist  is  broader  in  the  African  than 
in  the  European  ;  the  os  calcis  is  not  longer  in  negroes  than 
in  the  white  man,  the  larger  heel  of  the  former  being  simply 

due  to  an  expansion  of  the 
soft  parts. 

The  form  of  the  skull  va- 
ries greatly  in  the  different 
races,  and  even  in  individ- 
uals of   the   same  race   of 
mankind.     This  is  seen  in 
the  difference  of  HLQ  facial 
Fig.  sss.-skuii  of  a  Negro,  showing  its  angle.   This  is  obtained  by 
Pr0gnathi8m.-AfterOwen.  drawing  a  line   from   the 

occipital  condyle  along  the  floor  of  the  nostrils,  and  inter- 
secting it  by  a  second,  touching  the  most  prominent  parts 
of  the  forehead  and  upper  jaw ;  the  angle  they  make  is 
an  index  of  the  cranial  capacity,  and  of  the  degree  of  in- 
telligence of  the  individual.  The  facial  angle  in  the  reptiles 
is  very  slight,  as  it  is  in  the  birds  ;  in  the  dog  it  is  20°,  in  the 
gorilla  40°,  in  the  Australian  85%  in  the  civilized  Caucasian 
it  averages  95°,  while  the  Greek  sculptors  adopted  an  ideal 
angle  of  100°.  (Owen.*)  When  the  lower  part  of  the  face 
protrudes,  as  in  the  negro,  the  face  is  said  to  be  prognathous 
(Fig.  538)  ;  where  the  facial  angle  is  high,  and  the  face 
straight,  as  in  the  more  intellectual  forms,  the  cranium  is 

*  Pagenstecher  states  that  the  facial  angle  in  the  Caucasian  Euro- 
pean is  80°-85°,  and  even  over  90° ;  in  the  Mongolians  75°-80°  ;  in 
negroes  70°-75° ;  in  the  tribe  of  Makoias  in  South  Africa  64° ;  in  the 
tribe  of  Tikki-Tikki,  or  Akka  negroes,  the  dwarfs  described  by 
Schweinfurth,  only  60°.— Allgemeine  Zoologie,  i.,  p.  250. 


THE  VARIETIES   OF  MAN.  627 

said  to  be  orthognathous.  Those  skulls  which  are  high  and 
narrow,  i.e.,  with  the  longer  diameter  to  the  shorter,  as  100 
to  65,  are  said  to  be  dolichocephalic,  while  those  with  the 
diameters  as  100  to  85  are  called  br  achy  cephalic,  but  these  dis- 
tinctions have  been  found  to  be  quite  arbitrary. 

The  classification  of  the 'human  races  is  in  as  an  unsatis- 
factory state  as  that  of  the  domestic  animals.  Naturalists 
are  now  agreed  that  there  is  but  one  species  of  man.  Blu- 
menbach,  from  the  shape  of  the  skull  and  the  color  of  the 
skin,  divided  mankind  into  three  varieties,  the  white  or  Cau- 
casian, the  brown  or  Mongolian,  and  the  black  or  Ethiopian, 
considering  the  American  variety  as  connecting  the  Caucasian 
and  Mongolian,  and  the  Malayan  as  intermediate  between 
the  Caucasian  and  Ethiopian.  Hamilton  Smith  divided 
man  into  three  varieties,  Caucasian,  Mongolian,  and  Tropi- 
cal ;  Latham,  also,  into  three,  Japetidse,  Mongolidao,  and 
Atlantidae ;  and  Pickering  into  white,  brown,  and  black 
varieties,  with  intermediate  races.  Huxley  divides  the  dif- 
ferent races  into  two  primary  groups,  the  Ulotrichi,  with 
crisp  or  woolly  hair,  and  the  Leiotrichi  with  smooth  hair. 

The  average  height  of  Englishmen  is  5-8-5-10  feet  ;  in 
the  universities  more.  In  America,  the  average  height  of 
medical  and  military  men  is  5  •  9f  feet.  The  Patagonian  men 
are  nearly  six  feet  high  on  an  average;  the  women  5-10  feet; 
the  Bushman  and  Esquimaux  4-7,  the  latter  being  the  small- 
est people  on  the  earth.  The  smallest  dwarfs  in  Europe 
were  33  and  28  inches  in  height  respectively ;  while  Pat- 
rick Cotter,  the  Irish  giant,  was  8  feet  7  inches  tall. 

It  is  claimed  by  some  naturalists  that  man  has  descended 
from  some  generalized  type  of  animal  which  gave  rise  to 
several  series  of  forms  culminating  in  the  monkeys,  apes, 
and  man  respectively,  and  by  others  that  he  is  a  direct 
descendant  of  forms  like  the  chimpanzee  or  gorilla;  but 
it  is  probable  that  from  the  want  of  sufficient  data, 
the  question  as  to  the  origin  of  man  can  never  be  def- 
initely settled.  Setting  hypothesis  aside,  in  ascending 
the  mammalian  series,  we  have  seen  in  the  forms  lead- 
ing from  the  extinct  Eocene  generalized  types  of  Ed- 
ucalilia  to  the  Carnivora  and  Primates,  a  tendency  to 
an  extreme  specialization  of  those  parts  ministering  to  the 


628  ZOOLOGY. 

intellectual  behests  of  the  creature.  On  the  other  hand,  in 
all  general  points,  man's  limbs  are  those  of  the  primitive 
type  so  common  in  the  Eocene  Period.  As  Cope  remarks  : 
"He  is  plantigrade,  has  five  toes,  separate  carpals  and  tar- 
sals  ;  a  short  heel,  rather  flat  astragalus,  and  neither  hoofs 
nor  claws,  but  something  between  the  two.  The  bones  of 
the  fore  arm  and  leg  are  not  so  unequal  as  in  the  higher 
types  ;  and  remain  entirely  distinct  from  each  other,  and  the 
ankle  joint  is  not  so  perfect  as  in  many  of  them.  In  his 
teeth  his  character  is  thoroughly  primitive.  He  possesses,  in 
fact,  the  original  quadrituberculate  molar  with  but  little 
modification.  His  structural  superiority  consists  solely  in 
the  complexity  and  size  of  his  brain." 

Whether  man  in  common  with  other  animals  is  the  result 
of  divinely  ordered  processes  of  biological  laws,  appearing  at 
the  head  of  a  long  series  of  forms,  and,  as  probably  many 
other  animals  have,  with  comparative  suddenness,  being  at 
the  outset  in  all  essential  respects  man,  though  a  savage,  and 
not  with  a  long  pedigree  of  morphologically  impossible  Dar- 
winian "missing  links," — whether  he  thus  originated,  or  by 
an  independent  creative  act,  the  result  is  a  being  concerning 
whom  the  fact  that  he  is  physically  an  animal,  is  after  all  the 
least  important  characteristic  of  the  nature  of  him  who  is 
the  historian  of  his  own  and  other  species ;  who  is  capable 
of  studying  and  in  a  degree  comprehending  the  universe  in 
which  he  lives,  and  who  whatever  his  physical  origin  may 
have  been,  has  intellectual,  moral,  and  spiritual  capabilities 
which  render  his  nature  susceptible  of  endless  improvement, 
endowing  him  with  immortality  and  all  that  it  involves. 


CLASS  VII. — MAMMALIA. 

Body  covered  with  Mir  ;  young  nourished  with  milk  secreted  in  mam- 
ma; lower  jaw  articulating  directly  with  the  skull,  the  quadrate  lone  be- 
coming one  of  the  ear-bone*  (malleus) ;  a  diaphragm  dividing  the  body- 
cavity  into  thoracic  and  abdominal  portions  ;  heart  with  the  aorta  reflect- 
ed over  the  left  bronchus ;  blood-corpuscles  non-nucleated ;  brain  large, 
especially  the  cerebral  hemispheres  ;  viviparous;  uterine  gestation. 
Subclass  I.    Ornithodelphia. — Order  Monotremata. — Urinary  and  gen- 
ital   outlets  opening  into  the   cloaca.     (Echidna,  Ornitlio- 
rhynchus.) 


CLASSIFICATION  OF  MAMMALS.  629 

Subclass  II.   Didelphia. — Order  Marsupialia. — Mammals  with  a  mar- 
supium  and  bones  supporting  it.     (Macropus,  Didelphys.) 

Subclass  III.  Motwdephia. — Placental  mammals. 

Super-order  I.   Ineducabilia. — Brain  with   a    relatively   small, 
smooth  cerebrum. 

Order  1.  Bruta. — Incisors  absent ;  sometimes  toothless. 
(Bradypus.) 

Order  2.    Olires. — Rodents,  incisors  large.    (Sciurus.) 

Order  3.  Insectivora. — Fore  limbs  often  peculiarly  adapted 
for  burrowing  ;  molars  with  conical  cusps.  (Seal ops.) 

Order  4.  Chiroptera. — Fore  limbs  adapted  for  flight.  (Ves- 
pertilio.) 

Super-order  II.  Educdbilia. — Brain  with  a  relatively  large,  con- 
voluted  cerebrum. 

Order  5.  Cete. — Cetaceans ;  fish-like  in  form,  no  hind 
limbs.  (Balaena.) 

Order  6.  Sirenia. — Fish-like  in  form,  but  with  ascending 
rami  to  the  lower  jaw ;  teeth  ruminant-like.  (Mana- 
tus.) 

Order  1.  Proboscidea. — Snout  prolonged  into  a  proboscis. 
(Elephas.) 

Order  8.  Hyracoidea. — Long  curved  incisors;  feet  with 
pads ;  toes  encased  in  hoofs.  (Hyrax.) 

Order  9.  Toxodontia. — Extinct  forms,  with  well  developed 
incisors.  (Poxodon.) 

Order  10.  Ungulata.— Ungulates ;  toes  encased  in  hoofs. 
(Equus,  Bos.) 

Order  11.  Carnivora. — Teeth  pointed;  claws  large.  (Fell?, 
Canis.) 

Order  12.  Primates. — Brain  with  cerebrum  nearly  or  quite 
covering  the  cerebellum  ;  nails  usually  present ;  body 
quadrupedal,  quadrumanous,  or  erect  and  bimanous. 
(Cebus,  Gorilla,  Homo.) 

Laboratory  Work.— All  the  jcraniate  vertebrates  may  be  dissected  in 
the  same  general  manner,  either  under  water  in  pans,  or,  if  large,  upon 
the  dissecting  table.  The  necessary  tools  are  a  scalpel,  forceps,  scis- 
sors, and  tenaculum  or  hook  for  suspending  the  specimens  or  portions 


630 


ZOOLOGY. 


of  large  subjects  for  better  facility  in  dissecting.  A  small  sharp- 
pointed  narrow-bladed  scalpel,  besides  a  large  one,  curved,  as  well  as 
sharp-pointed  scissors  are  useful,  with  a  German  silver  blow-pipe 
for  temporarily  distending  vessels ;  and  also  a  blunt-pointed  copper 
wire  or  probe  made  for  surgeon's  use,  will  be  necessary.  All  these  in- 
struments, put  up  in  a  compact  box,  can  be  purchased  at  the  surgical 
instrument  maker's,  as  well  as  syringes  for  injecting  the  circulatory 
organs  and  vascular  parts  of  the  viscera. 

TABULAR  VIEW  OP  THE  SEVEN  CLASSES  OF  VERTEBRATES. 


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SUB-BRANCH  II.— CRANIOTA 


SUB-BRANCH  I.— ACRANIA. 


I.  LEPTOCARDII  (Lancelot). 


CHAPTER   IX. 

COMPARATIVE  ANATOMY  OF  ORGANS. 

HAVIKG  studied  the  morphology  of  animals  in  a  system- 
atic way,  it  will  be  well  for  the  student  to  make  a  brief  TC- 
view  of  those  facts  stated  in  the  foregoing  chapters  bearing 
on  the  origin  and  successive  degrees  of  complication  of  the 
most  important  organs. 

Organs  of  Digestion— The  Mouth  and  Teeth. — The  most 
important  organs  in  the  animal  system  are  those  relating  to 
digestion,  as  an  animal  may  respire  solely  through  its  body- 
walls,  or  do  without  a  circulatory  or  nervous  system,  but 
must  eat  in  order  to  live  and  grow.  The  opening  by  which 
the  food  is  taken  into  the  alimentary  canal  is  called  the 
mouth,  whether  reference  is  made  to  the  "  mouth"  of  a 
hydra  or  of  a  vertebrate  ;  although  the  structure  of  the  edges 
may  differ  radically,  still  in  all  Metazoa  the  mouth  is  due  to 
an  inpushing  of  the  ectoderm,  however  differently  the 
edge  of  the  mouth  may  be  supported  and  elaborated.  The 
edges  of  the  mouth  are  usually  called  the  lips,  but  true  lips 
for  the  first  time  appear  in  the  Mammalia.  The  trituration 
or  mastication  of  the  food  is  accomplished  among  the  in- 
vertebrates in  a  variety  of  ways,  and  by  organs  not  always 
truly  homologous. 

Hard  bodies  serving  as  teeth  occur  for  the  first  time  in  the 
animal  series  in  the  sea-urchins,  where  a  definite  set  of  cal- 
careous dental  processes  or  teeth  (Figs.  78  and  79),  with  solid 
supports  and  a  complicated  muscular  apparatus,  serves  for 
the  comminution  of  the  food,  which  consists  of  decaying  an- 
imals and  sea- weeds.  In  those  Echinoderms  which  do  not 
have  a  solid  framework  of  teeth,  the  food  consists  of  minute 
forms  of  life,  protozoans  and  higher  soft-bodied  animals, 


632  ZOOLOGY. 

or  the  free-moving  young  of  higher  animals,  which  are 
carried  into  the  mouth  in  currents  of  water  or  swallowed 
bodily  with  sand  or  mud. 

Among  the  worms  true  organs  of  mastication  for  the  first 
time  appear  in  the  Rotatoria  (Fig.  122),  where  the  food,  such 
as  infusoria,  etc.,  is  crushed  and  is  partly  comminuted  by 
the  well-marked  horny  or  chitinous  pieces  attached  to  the 
mastax.  In  most  other  low  worms  the  mouth  is  unarmed. 
In  the  leeches  there  are  three,  usually  in  the  annelids  two, 
denticulated  or  serrate,  chitinous  flattened  bodies  situated 
in  the  extensible  pharynx  of  these  worms,  and  suited  for 
seizing  and  crushing  their  prey. 

In  the  higher  mollusks,  such  as  the  snails  (Ceplialoplwra) 
and  cuttles,  besides  broad  thin  pharyngeal  teeth,  compara- 
ble with  those  mentioned  as  existing  in  the  worms,  is  the  lin- 
gual ribbon  already  described  (p.  276,  Fig.  215.),  and  admira- 
bly adapted  for  sawing  or  slicing  sea- weeds  and  cutting 
and  boring  into  hard  shells,  acting  somewhat  like  a  lapi- 
dary's wheel  ;  this  organ,  however,  is  limited  in  its  action, 
and  in  the  cuttles  the  jaws,  which  are  like  a  parrot's  beak, 
do  the  work  of  tearing  and  biting  the  animals  serving  as 
food,  which  are  seized  and  held  in  place  by  the  suckered 
arms. 

In  the  crustaceans  and  insects  we  have  an  approach  to 
true  jaws,  but  here  they  work  laterally,  not  up  and  down  or 
vertically,  as  in  the  vertebrate  jaws  ;  the  mandibles  of  these 
animals  are  modified  feet,  and  the  teeth  on  their  edges  are 
simply  irregularities  or  sharp  processes  adapting  the  mandi- 
bles for  tearing  and  comminuting  the  food.  It  is  generally 
stated  that  the  numerous  teeth  lining  the  crop  of  Crustacea 
and  insects  (Fig.  282)  serve  to  further  comminute  the  food 
after  being  partially  crushed  by  the  mandibles,  but  it  is  now 
supposed  that  these  numerous  points  also  act  collectively  as 
a  strainer  to  keep  the  larger  particles  of  food  from  passing 
into  the  chyle-stomach  until  finely  crushed. 

The  king-crab  burrows  in  the  mud  for  worms  (Nereids, 
etc. )  ;  these  may  be  found  almost  entire  in  the  intestine, 
having  only  been  torn  here  and  there  and  partly  crushed  by 
the  spines  of  the  base  of  the  foot-jaws,  which  thus  serve  the 


COMPARATIVE  ANATOMY  OF  ORGANS.  633 

purpose  effected  by  the  serrated  edges  of  the  mandibles  of 
the  genuine  Crustacea  and  insects. 

Among  vertebrates,  the  lancelet  is  no  better  off  than  the 
majority  of  the  Coelenterates  and  worms,  having  no  solid 
parts  for  mastication  ;  and  we  have  seen  that  the  jaws  and 
teeth  of  the  hag- fish  and  even  the  lamprey  eel  form  a  very 
different  apparatus  from  the  jaws  and  its  skeleton  in  the 
higher  vertebrates  ;  and  that,  even  in  the  latter,  the  bony 
elements  differ  essentially  in  form  in  the  different  classes, 
though  originating  in  the  same  manner  in  embryonic  life. 
In  the  birds  we  have  seen  that  the  mandible  and  maxilla  are 
encased  in  horny  plates,  that  true  teeth  are  remarkably  ex- 
ceptionable, the  gizzard  being,  however,  provided  with  two 
hard  grinding  surfaces  ;  on  the  other  hand,  mammals  with- 
out teeth  are  exceptionable. 

The  teeth  of  fishes  are  developed,  not  only  in  the  jaws, 
but  on  the  different  bones  projecting  from  the  sides  and 
roof  of  the  mouth,  and  extend  into  the  throat.  In  many 
cases,  in  the  bony  fishes,  these  sharp  recurved  teeth  serve  to 
prevent  the  prey,  such  as  smaller  fish,  from  slipping  out  of 
the  mouth.  On  the  other  hand,  the  upper  and  lower  sides 
of  the  mouth  of  certain  rays  (Myliobatis)  are  like  the  solid 
pavement  of  a  street,  and  act  as  an  upper  and  nether  mill- 
stone to  crush  solid  shells. 

In  the  toothless  ant-eaters  the  food  consists  of  insects, 
which  are  swallowed  without  being  crushed  in  the  mouth  ; 
true  teeth  in  the  duckbill  are  wanting,  their  place  being 
taken  by  the  horny  processes  of  the  jaws,  while  in  Steller's 
manatee  the  toothless  jaws  are  provided  with  horny  solid 
plates  for  crushing  the  leaves  of  aquatic  succulent  plants. 
Examples  of  the  most  highly  differentiated  teeth  in  verte- 
brates are  seen  in  those  animals,  like  the  bear,  whose  food  is 
omnivorous,  consisting  of  flesh,  insects,  and  berries,  where 
the  crown  of  the  molars  are  tuberculate;  while  the  canines  are 
adapted  for  holding  the  prey  firmly  as  well  as  for  tearing  the 
flesh,  and  the  incisors,  for  both  cutting  and  tearing  the  food. 

The  simplest  form  of  a  genuine  digestive  or  enteric  canal 
is  to  be  found  in  the  Hydra,  and  in  a  more  advanced  stage 
in  the  marine  Hydroids.  For  the  technical  name  of  the 


634  ZOOLOGY. 

digestive  tract  we  may  adopt  Haeckel's  term  enter  on.  In 
the  jelly-fishes  the  stomach  opens  into  four  or  more  water- 
vascular  canals  or  passages,  by  which  the  food,  when  par- 
tially digested  and  mixed  with  sea-water,  thus  forming  a 
rude  sort  of  blood,  supplies  the  tissues  with  nourishment. 
In  the  sea-anemones  and  coral  polyps,  the  digestive  cavity  is 
still  more  specialized,  and  its  walls  are  partly  separated  from 
the  walls  of  the  body,  though  at  the  posterior  end  the 
stomach  opens  directly  into  the  body-cavity.  In  the  Echi- 
noderms  and  worms  do  we  find  for  the  first  time  a  genuine 
digestive  tube,  lying  in  the  perivisceral  space  (which,  with 
Haeckel,  we  may  call  the  cesium},  and  opening  externally 
for  the  rejection  of  waste  matter. 

In  the  worms  the  digestive  canal  now  becomes  separated 
into  a  mouth,  an  oesophagus,  with  salivary  glands  opening 
into  the  mouth,  and  there  is  a  division  of  the  digestive  tract 
into  three  regions — i.e.,  fore  (oesophagus),  middle  (chyle- 
stomach),  and  hind  (intestine)  enteron.  In  the  mollusks 
and  higher  worms  there  is  a  well-marked  sac-like  stomach 
and  an  intestine, with  a  liver,  present  in  certain  worms  (in 
the  ascidians  and  mollusks),  opening  into  the  beginning  of 
the  intestine.  All  these  divisions  of  the  digestive  tract  ex- 
ist still  more  clearly  in  the  Crustacea  and  most  insects.  In 
the  latter,  six  or  more  excretory  tubes  (Malpighian  vessels) 
discharge  their  contents  into  the  intestines,  and  in  the  "  res- 
piratory tree  "  of  the  Holothurian  and  the  excretory  vessels 
of  certain  worms  we  have  organs  with  probably  similar  uses. 

In  the  vertebrates,  from  the  lancelet  to  man,  the  alimen- 
tary canal  has,  without  exception,  the  three  divisions  of  oes- 
ophagus, stomach,  and  intestine,  with  a  liver.  In  this  branch 
the  lungs  are  either,  as  in  the  lancelet,  modified  parts  of 
the  first  division  of  the  digestive  tract  or  originally  sac-like 
dilatations  of  the  digestive  tract.  The  intestine  is  also 
subdivided  in  the  mammals  into  the  small  and  large  intestine 
and  rectum,  a  coecum  being  situated  at  the  limits  between 
the  small  and  large  intestine.  We  thus  observe  a  gradual 
advance  in  the  degree  of  specialization  of  the  digestive  or- 
gans corresponding  to  the  degree  of  complication  of  the  an- 
imal. 


COMPARATIVE  ANATOMY  OF  ORGANS,  635 

Organs  of  Circulation. — Intimately  associated  with  the 
digestive  canal  are  the  vessels  in  which  the  products  of  di- 
gestion mix  with  the  blood  and  supply  nourishment  for  the 
tissues,  or,  in  other  words,  for  the  growth  of  the  body.  In 
the  Infusoria  the  evident  use  of  the  contractile  vesicles  is  to 
aid  in  the  diffusion  of  the  partly  digested  food  of  these  mi- 
croscopic forms.  In  the  Hydra  the  food-stuff  is  directly 
taken  up  by  the  cells  lining  the  ccelum,  while  the  imper- 
fectly formed  blood  also  finds  access  to  the  hollows  of  the 
tentacles.  The  mode  in  which  the  cells  lining  the  canals 
in  the  sponge  take  up,  by  means  of  the  large  cilia,  micro- 
scopic particles  of  food,  directly  absorbing  them  in  their 
substance,  is  an  interesting  example  of  the  mode  of  nourish- 
ment of  cellular  tissues  of  the  lower  animals. 

The  sea-anemone  presents  a  step  in  advance  in  organs  of 
circulation  ;  here  the  partly  digested  food  escapes  through 
the  open  end  of  the  stomach  into  the  peri  visceral  chambers, 
the  action  of  the  cilia,  with  the  contractions  of  the  body, 
churning  the  blood,  consisting  of  sea- water  and  the  particles 
of  digested  food,  and  a  few  blood-corpuscles,  hither  and 
thither,  and  forcing  it  into  every  interstice  of  the  body, 
even  into  the  tentacles,  so  that  the  tissues  are  everywhere 
supplied  with  food. 

The  water-vascular  system  of  the  Coelenterates  presents  an 
additional  step  in  degree  of  complexity  ;  but  it  is  not  until 
we  reach  the  Echinoderms  on  the  one  hand,  and  such 
worms  as  the  Nemertes  and  allies  on  the  other,  where  defi- 
nite tubes  or  canals,  the  larger  ones  contractile,  and  in  the 
latter  type  at  least  formed  from  the  mesoderm,  serve  to 
convey  a  true  blood  to  the  various  parts  of  the  body,  that 
we  have  a  definite  blood  system.  In  the  Echinoderms  a 
true  haemal  or  vascular  system  may  co-exist  with  the  water- 
vascular  system.  In  the  annelids,  such  as  the  Nereis,  one 
of  the  blood-vessels  may  be  modified  to  form  a  pulsating 
tube  or  "  heart,"  by  which  the  blood  is  directly  forced  out- 
ward to  the  periphery  of  the  body  through  vessels  which  may, 
by  courtesy,  be  called  arteries,  while  the  blood  returns  to 
the  "  heart  "  by  so-called  veins. 

The  mollusks  have  a  circulatory  system  which  presents  a 


636  ZOOLOGY. 

nearer  approach  to  the  vertebrate  heart  and  its  vessels  than 
even  the  crustaceans  and  insects,  for  the  ventricle  and  one  or 
two  auricles,  with  the  complicated  arterial  and  venous  sys- 
tem of  vessels  of  the  clam,  snail,  and  cuttle-fish,  truly  fore- 
shadow the  genuine  heart  and  systemic  and  pulmonary  cir- 
culation of  the  vertebrates.  The  mollusks,  and  king-  crab, 
and  the  lobster  present  some  approach  to  the  capillaries  of 
vertebrates.  The  circulation  in  certain  worms,  from  Ne- 
mertes  upward,  may  be  said  to  be  closed,  the  vessels  being 
continuous  ;  but  they  are  not  so  in  insects,  where  true  veins 
are  not  to  be  found,  the  blood  returning  to  the  heart  in 
channels  or  lacunae  in  the  spaces  between  the  muscles  and 
viscera. 

We  have  seen  that  in  vertebrates  the  "  aortic  heart  "  of  the 
lancelet  or  Amphioxus  is  simply  a  pulsating  tube,  and  there 
are  portions  of  other  vessels  which  are  pulsatile,  so  that 
there  is,  as  in  sotne  worms,  a  system  of  "hearts."  A  gen- 
uine heart,  consisting  of  an  auricle  and  a  ventricle  only,  first 
appears  in  the  lamprey.  This  condition  of  things  survives 
in  fishes,  with  the  exception  of  those  forms,  such  as  the  lung- 
fish  (Dipnoans),  whose  heart  anticipates  in  structure  that  of 
the  amphibians  and  reptiles,  in  which  a  second  auricle  ap- 
pears. Again,  certain  reptiles,  such  as  the  crocodiles,  antici- 
pate the  birds  and  mammals  in  having  two  ventricles  —  i.e., 
a  four-chambered  heart.  It  should  be  borne  in  mind  that 
in  early  life  the  heart  of  all  skulled  vertebrates  (Craniota) 
is  a  simple  tube,  and  as  Gegenbaur  states,  "  as  it  gradually 
gets  longer  than  the  space  set  apart  for  it,  it  is  arranged  in 
an  S-shaped  loop,  and  so  takes  on  the  form  which  the  heart 
has  later  on."  Owing  to  this  change  of  form,  it  is  divided 
into  two  parts,  the  auricle  and  ventricle. 

A  striking  feature  first  encountered  in  the  craniate  ver- 
tebrates is  the  presence  of  a  set  of  vessels  conveying  the 
nutrient  fluid  or  chyle  which  filters  through  the  walls  of 
the  digestive  canal  to  the  blood-vessels  ;  these  are  the  lym- 
phatics. In  the  lancelet,  as  well  as  in  the  invertebrate  ani- 
mals, such  vessels  do  not  occur,  but  the  chyle  oozes  through 
the  stomach-walls  and  directly  mixes  with  the  blood. 


HE 

ERSITY 


COMPARATIVE  ANATOMY  OF  ORGANS.          637 

Organs  of  Respiration. — Always  in  intimate  relation  with 
the  circulatory  system  are  the  means  of  respiration.  The 
process  may  be  carried  on  all  over  the  body  in  the  simple 
animals,  such  as  Protozoa  or  sponges,  or,  as  in  Ccelenterates, 
it  may  be  carried  on  in  the  water-vascular  tubes  of  those 
animals,  while  in  the  so-called  te  respiratory  tree"  of  Echin- 
oderms  it  may  go  on  in  company  with  the  performance  of 
other  functions  by  the  same  vessels.  Respiration,  however, 
is  inclined  to  be  more  active  in  such  finely  subdivided  parts 
of  the  body  as  the  tentacles  of  polyps,  of  worms,  or  any 
filamentous  subdivisions  of  any  of  the  invertebrates  ;  these 
parts,  usually  called  gills,  though  only  the  gills  of  fishes  are 
truly  such,  present  in  the  aggregate  a  broad  respiratory  sur- 
face. Into  the  hollows  of  these  filamentous  processes, 
which  are  usually  extensions  of  the  body-walls,  blood  is 
driven  through  vessels,  and  the  oxygen  in  the  water  bathing 
the  gills  filters  through  the  integument,  and  immediately 
gains  access  to  and  mixes  with  the  blood. 

The  gills  of  the  lower  animals  appear  at  first  sight  as  if 
distributed  over  the  body  in  a  wanton  manner,  appearing 
in  some  species  on  the  head,  in  others  along  the  sides  of  the 
body,  or  in  others  on  the  tail  alone  ;  but  in  fact  they  always 
arise  in  such  situations  as  are  best  adapted  to  the  mode  of 
life  of  the  creature. 

The  gills  of  many  of  the  lower  animals  afford  an  admira- 
ble instance  of  the  economy  of  nature.  The  tentacles  of 
polyps,  polyzoans,  brachiopods,  and  many  true  worms  serve 
also,  as  delicate  tactile  organs,  for  grasping  and  conveying 
food  to  the  mouth,  and  often  for  locomotion.  The  suckers 
or  "  feet"  of  star-fish  or  sea-urchins  also  without  doubt 
perform  the  office  of  gills,  for  the  luxuriously  branched, 
beautifully-colored  tentacles  of  the  sea-cucumber  are  simply 
modifications  of  the  ambulacral  feet.  One  of  the  readiest 
ways  of  judging  of  the  mental  condition,  so  to  speak,  of  a 
worm,  such  as  Sabella  or  Terebrella  or  of  a  polyzoon  or  a 
brachiopod,  is  to  watch  the  movements  of  their  beautiful 
delicate  gills,  which  are  thrust  in  or  out,  waved  hack  and 
forth,  slowly  or  suddenly,  according  to  the  degree  of  tran- 
quillity or  disquietude  of  their  possessors. 


638  ZOOLOGY. 

In  the  mollusks,  especially  the  snails  and  cuttle-fish,  the 
gills  are  in  close  relations  with  the  heart,  so  that  in  the  cut- 
tle-fish the  auricles  are  called  "branchial  hearts."  The 
gills  of  crustaceans  (Fig.  259)  are  attached  either  to  the 
thoracic  legs  or  are  modified  abdominal  feet,  being  broad, 
thin,  leaf -like  processes,  into  which  the  blood  is  forced  by 
the  contractions  of  the  tubular  heart.  Respiration  in  the 
insects  goes  on  all  over  the  interior  of  the  body,  the  tracheal 
tubes  distributing  the  air  so  that  the  blood  becomes  oxyge- 
nated in  every  part  of  the  body,  including  the  ends  of  all  the 
appendages.  The  gills  of  aquatic  insects  are  in  all  cases  fila- 
mentous or  leaf -like  expansions  of  the  skin  permeated  by 
tracheae  (Fig.  326)  ;  they  are,  therefore,  not  strictly  homolo- 
gous with  the  gills  of  crustaceans  or  of  worms. 

The  gills  of  fishes  are  so  situated  as  to  be  constantly 
bathed  by  fresh,  water  ;  in  the  amphibians  and  lung- fishes, 
lungs,  which  are  outgrowths  of  the  enteric  canal,  replace  the 
air-sacs  of  the  fishes,  the  air  being  now  swallowed  by  the 
mouth  and  gaining  access  by  a  special  duct,  the  larynx,  to 
highly  specialized  organs  of  respiration,  the  lungs,  which 
are  situated  in  the  thoracic  cavity  near  the  heart. 

The  Nervous  System.— We  have  seen  that  animals  of  com- 
paratively complicated  structure  perform  their  work  in  the 
animal  economy  without  any  nervous  S3Tstem  whatever.  It 
has  been  only  recently  discovered  that  in  a  few  jelly-fish  is 
there,  for  the  first  time  in  the  animal  series,  a  consecutive 
nervous  system,  with  definite  nerve-centres  or  ganglia.  In 
most  Acalephs  none  has  been  found,  so  that  the  majority 
of  Coelenterates  perform  their  complicated  movements, 
swimming  about  for  food,  taking  it  in,  digesting  it,  and  re- 
producing their  kind,  without  the  aid  of  what  seems,  when 
we  study  vertebrates  alone,  as  the  most  important  and 
fundamental  system  of  organs  in  the  body. 

The  Protozoa,  sponges,  and  most  Coelenterates  depend,  for 
the  power  of  motion,  on  the  contractility  of  the  protoplasm 
of  the  body,  whether  or  not  separated  into  muscular  tissue. 
In  the  Hydra  for  the  first  time  appear  the  traces  of  a  ner- 
vous tissue  in  the  so-called  nervo-muscular  cells,  one  por- 


COMPARATIVE  ANATOMY  OF  ORGANS.  639 

tion  of  a  cell  being  muscular,  the  other  nervous  in  its  func- 
tions. 

A  more  definite  nervous  organization  is  the  disconnected 
bodies  and  rod-like  nerve-cells,  and  other  nervous  bodies 
found  near  the  eye-spots,  and  the  nerve-cells  and  fibres  at 
the  base  of  the  sea-anemone  ;  but,  as  has  been  stated,  a  gen- 
uine nervous  system  for  the  first  time  appears  in  certain 
naked-eyed  jelly-fishes,  in  which  it  is  circular,  sharing  the 
radiated  disposition  of  parts  in  these  animals.  The  Echin- 
oderms  have  a  well-developed  nervous  system,  consisting  of 
a  ring  (without,  however,  definite  ganglia,  though  masses  of 
ganglionic  cells  are  situated  in  the  larger  nerves),  surround- 
ing the  oesophagus,  and  sending  a  nerve  into  each  arm  ;  or  in 
the  Holothurians  situated  under  the  longitudinal  muscles 
radiating  from  that  muscle  closing  the  mouth. 

In  all  other  invertebrate  animals,  from  the  worms  and 
mollusca  to  the  crustaceans  and  insects,  the  nervous  system 
is  fundamentally  built  upon  the  same  plan.  There  is  a  pair 
of  ganglia  above  the  oesophagus  called  the  "  brain  ;"  on  the 
under  side  is  usually  a  second  pair  ;  the  four,  with  the  nerves 
or  commissures  connecting  them,  forming  a  ring.  This  ar- 
rangement of  ganglia,  often  called  the  "  oesophageal  ring," 
constitutes,  with  the  slender  nerve-threads  leading  away  from 
them,  the  nervous  system  of  the  lower  worms,  in  many  of 
which,  however,  as  also  in  the  Polyzoa  and  Brachiopoda, 
the  subcesophageal  ganglia  are  wanting.  Now  to  the 
oesophageal  ring  with  its  two  pairs  of  ganglia  add  a  third 
pair  of  visceral  ganglia,  and  we  have  the  nervous  system 
of  the  clam  and  many  mollusks.  In  the  higher  ringed 
worms,  the  Anniilata,  and  in  the  Crustacea  and  Insects,  a 
chain  of  ganglia,  or  brains,  which  is  ventral,  lying  on  the 
floor  of  the  coelum  or  body-cavity,  completes  the  highest 
form  of  nerve-centre  found  in  the  invertebrate  animals, 
unless  we  except  the  mass  of  ganglia,  partly  enclosed  in  an 
imperfect  cartilaginous  capsule  of  the  Cephalopods,  which 
hints  at  the  brain  and  skull  of  Vertebrates.  The  nervous 
cord  of  the  Appendicularia,  an  Ascidian,  is  constructed  on 
the  same  plan  as  in  the  Annulata,  but  the  mode  of  origin  and 
apparently  dorsal  position  of  the  nervous  system  of  the 


640  ZOOLOUY. 

tailed  larval  Ascidian  presents  features  which  apparently 
anticipate  the  state  of  things  existing  among  the  lower  ver- 
tebrates, such  as  the  lancelet. 

In  the  last-named  animal  the  nervous  cord  has  a  dorsal 
position — i.e.,  rests  above  the  alimentary  canal ;  but  as  yet 
no  brain  appears,  only  a  very  slight  enlargement  of  the  an- 
terior end  of  the  nervous  cord  from  which  a  few  nervous  - 
threads  are  distributed  to  minute  sense-organs  in  the  head. 
In  all  the  craniate  Vertebrates,  from  the  lamprey  upward, 
the  brain  is  a  series  of  close-set  ganglia,  having  a  definite 
site,  enclosed  by  a  skull  or  brain-box,  and  with  definite  re- 
lations to  the  sense-organs.  Attention  has  already  been 
given  in  a  general  way,  in  the  foregoing  pages,  to  the  increas- 
ing complexity  of  the  brain,  especially  to  the  relative  size 
and  markings  of  the  cerebral  hemispheres  and  cerebellum, 
as  we  rise  from  the  fish  to  man. 

Organs  of  Sense.— While  all  animals,  perhaps  without 
exception,  unless  it  be  the  root-barnacles,  and  a  few  other 
parasitic  forms,  have  the  sense  of  touch,  which,  in  the  lower 
Protozoa  is  so  slight  as  to  be  compared  with  the  contractility 
common  to  all  living  protoplasmic  matter,  whether  existing 
in  cellular  tissue  or  one-celled,  independent  animals  ;  not  all 
of  the  lower  animals  have,  however,  definite  sense-organs. 

The  Eye.— The  most  important  of  these  are  undoubtedly 
eyes,  as  they  are  the  most  commonly  met  with.  The  sim- 
plest form  of  eyes  are  perhaps  those  of  the  sea-anemone,  in 
which  there  are,  besides  pigment  cells  forming  a  colored 
mass,  refractive  bodies  which  may  break  up  the  rays  of  light 
impinging  on  the  pigment  spot,  so  that  these  creatures  may 
be  able  to  distinguish  light  from  darkness.  The  next  step 
in  advance  is  where  a  pigment  mass  covers  a  series  of  refract- 
ive cells  called  "  crystalline  rods  "  or  "  crystalline  cones," 
Avhich  are  situated  at  the  end  of  a  nerve  proceeding  from 
the  "  brain."  Such  simple  eyes  as  these,  often  called  "  eye- 
spots,"  may  be  observed  in  the  flat  worms,  and  they  form 
the  temporary  eyes  of  many  larval  worms,  Echinoderms 
and  mollusks.  In  some  nemertean  worms,  such  as  certain 
species  of  Polia  and  Nemertes,  true  eyes  appear,  but  in  the 
ringed  worm,  Neoplianta  celox,  Greef  describes  a  remarka- 


COMPARATIVE  ANATOMY  OF  ORGANS.  641 

bly  perfect  eye,  consisting  of  a  projecting  spherical  lens 
covered  by  the  skin,  behind  which  is  a  vitreous  body,  a 
layer  of  pigment  separating  a  layer  of  rods  from  the  exter- 
nal part  of  the  retina,  outside  of  which  is  the  expansion  of 
the  optic  nerve.  Eyes  are  also  situated  on  the  end  of  the 
body  in  some  worms,  and  in  a  worm  called  Polyophthalmus 
each  segment  of  the  body  bears  a  pair  of  eyes. 

The  eyes  of  mollusks  are,  as  a  rule,  highly  organized,  un- 
til in  the  cuttle-fish  the  eye  becomes  nearly  as  highly  de- 
veloped as  in  fishes,  but  still  the  eye  of  the  cuttle-fish  is  not 
homologous  with  that  of  Vertebrates,  since  in  the  former 
the  crystalline  rods  are  turned  toward  the  opening  of  the 
eye,  while  in  Vertebrates  they  are  turned  away  from  the 
opening  of  the  eye,  so  that,  as  Huxley  as  well  as  Gegen- 
baur  show,  the  resemblance  between  the  eye  of  the  Ce- 
phalopods  and  of  the  Vertebrates  is  a  superficial  one. 

While,  as  we  have  seen,  the  eyes  of  the  worms  and  the 
mollusks  are  situated  arbitrarily,  by  no  means  invariably 
placed  in  the  head,  in  the  Crustaceans  the  eyes  assume  in 
general  a  definite  position  in  the  head,  except  in  a  schizo- 
pod  crustacean  (Euphausia),  where  there  are  eye-like  organs 
on  the  thorax  and  abdomen.  In  insects  there  are  both  sim- 
ple and  compound  eyes  occupying  definitely  the  upper  and 
front  part  of  the  head. 

The  eyes  of  the  lancelet  are  not  homologous  with  those 
of  the  higher  Vertebrates,  being  only  minute  pigment  spots 
comparable  with  those  of  the  worms.  In  the  skulled  Ver- 
tebrates the  eyes  are  of  a  definite  number,  and  in  all  the 
types  occupy  a  definite  position  in  the  head. 

The  Ear.— The  simplest  kind  of  auditory  organ  is  to  be 
found  in  jelly-fishes,  where  an  organ  of  hearing  first  occurs. 
In  these  animals,  situated  on  the  edge  of  the  disk,  are  minute 
vesicles  containing  one  or  more  concretionary  bodies  or 
crystals.  Reasoning  by  exclusion,  these  are  supposed  to  rep- 
resent the  ear-vesicles  or  otocysts  of  worms  and  mollusks  ; 
and  the  concretions  or  crystals,  the  otoliths  of  the  same  kind 
of  animals. 

The  otocysts  or  simple  ears  of  worms  and  mollusks  are 
minute  and  usually  difficult  to  find,  especially  the  auditory 


643  ZOOLOGY. 

nerve  leading  from  them  to  the  nerve-centres.  In  the 
clam  it  is  to  be  looked  for  in  the  so-called  foot.  In  the 
snails  the  auditory  vesicles  are  placed  in  the  head  close  to 
the  brain,  as  also  in  cuttle-fish.  The  ears  of  Crustacea  are 
sacs  formed  by  inpushings  of  the  integument  filled  with  fluid, 
into  which  hairs  project,  and  which  contain  grains  of  sand 
which  have  worked  in  from  the  outside,  or  concretions  of 
lime.  These  are  situated  in  the  shrimps  and  crabs  at  the 
base  of  the  inner  antennae,  but  in  certain  other  lower  Crusta- 
cea, as  in  Mysis,  they  are  placed  at  the  base  of  the  lobes 
of  the  tail.  In  the  insects  the  ear  is  a  sac  covered  by  a 
tympanum,  with  a  ganglionic  cell  within,  leading  by  a 
slender  nerve-fibre  to  a  nerve-centre,  and  in  these  animals 
the  distribution  of  ears  is  very  arbitrary.  In  the  locust  they 
are  situated  at  the  base  of  the  abdomen  (Fig.  279)  ;  in  the 
green  grasshoppers  or  katydids  and  the  crickets  in  the  fore 
tibiae  ;  and  it  is  probable  that  in  the  butterflies  the  antennae 
are  organs  of  hearing. 

The  vertebrate  ears  are  two  in  number  and  occupy  a  dis-. 
tinct,  permanent  position  in  the  skull,  however  much  modi- 
fied the  middle  and  outer  ear  become. 

Organs  of  Smell.— The  sense  of  smell  is  obscurely  indi- 
cated by  special  organs  in  the  invertebrate  animals,  nasal 
organs  as  such  being  characteristic  of  the  skulled  Vertebrates. 
Whether  organs  of  smell  exist  in  any  worms  or  not  is  un- 
known ;  there  are  certain  pits  in  some  worms  which  may 
possibly  be  adapted  for  detecting  odors.  In  some  insects  at 
least  the  organs  of  smell  are  without  doubt  well  developed  ; 
the  antennas  of  the  burying  beetles  are  large  and  knob-like, 
and  evidently  adapted  for  the  detection  of  carrion.  It  is 
possible  that  certain  organs  situated  at  the  base  of  the  wings 
of  the  flies  and  on  the  caudal  appendages  of  the  cockroach 
and  certain  flies  (Fig.  290)  are  of  use  in  detecting  odors. 


CHAPTER  X. 

DEVELOPMENT  AND  METAMORPHOSES  OF  ANT- 

MALS. 

Embryology.— The  development  of  the  individual  is  often 
an  epitome  of  the  classification  of  the  order  or  class  to  which 
it  belongs,  as  well  as  of  the  development  or  appearance  in 
geological  history  of  the  different  members  of  the  order  or 
class  to  which  the  individual  belongs.  The  changes  under- 
gone by  the  animal  within  the  egg  are  often  so  sudden  and 
marked  that  the  separate  chapters  of  its  history  as  an  em- 
bryo can  be  read  side  by  side  with  the  history  of  the  succes- 
sion of  the  different  genera  and  families  of  its  type  in  past 
ages.  Moreover,  it  is  now  generally  supposed  by  naturalists 
that  these  critical  periods  in  the  development  of  the  individ- 
ual have  a  constant  relation  to  external  causes  which  have 
acted  on  the  ancestors  of  the  animal,  and  hence  that  these 
changes  are  the  result  of  influences  and  changes  in  the  sur- 
roundings of  the  forms  which  have  preceded.  So  much  in- 
terest, therefore,  attaches  to  the  subject  of  the  early  develop- 
ment of  animals,  that  much  prominence  has  in  the  foregoing 
pages  been  given  to  the  matter. 

We  may  now  briefly  review  the  more  striking  phenomena 
of  development  in  the  invertebrate  animals,  and  close  with  a 
summary  of  the  mode  of  development  of  Vertebrates. 

The  eggs  of  all  animals  consist  of  three  portions,  the  egg 
proper,  consisting  of  a  mass  of  protoplasm  enveloped  by 
the  yolk  or  food-stuff,  the  nucleus  or  germinative  vesicle, 
and  the  nucleolus  or  germinative  spot. 

Before  the  egg  is  ready  for  fertilization  it  undergoes  a 
special  process  of  maturation,  involving  the  following  series 


044  ZOOLOGY. 

of  events  :  1.  Transportation  of  the  germinal  vesicle  to  the 
surface  of  the  egg  ;  2.  An  absorption  of  the  membrane  of 
the  nucleus  or  germinative  vesicle  and  a  change  in  the  ger- 
minative  spot  ;  3.  The  portion  of  the  nucleus  surviving  as- 
sumes a  spindle-shape,  this  portion  being  largely  formed 
from  the  nucleolus  ;  4.  One  end  of  the  spindle  enters  into  a 
protoplasmic  prominence  at  the  surface  of  the  egg  ;  5.  The 
spindle  divides  into  two  halves,  one  remaining  in  the  egg, 
the  other  in  the  prominence,  the  latter  separating  from  the 
egg  and  forming  the  polar  cell  ;  6.  A  second  polar  cell  forms 
in  the  same  manner  as  the  first,  part  of  the  spindle  still  re- 
maining in  the  egg  ;  7.  The  part  of  the  spindle  remaining 
in  the  egg,  after  the  formation  of  the  second  polar  cell,  is 
converted  into  a  nucleus,  the  female pronucleus,  and  finally, 
just  before  fertilization,  the  female  pronucleus  takes  its  po- 
sition at  the  centre  of  the  egg. 


Fig.  539.— Development  of  the  sperm-cells  of  a  blind  worm  (Epicrium  glutinosum). 
a,  teetis-cell ;  ft,  the  same,  more  numerous  ;  c,  d,  e,  becoming  more  numerous  and 
finally  forming  spermatozoa  (/).  Highly  magnified.— After  Minot. 

After  this,  the  first  step  in  the  development  of  many-celled 
animals  is  the  fusion  of  the  protoplasm  of  the  female  pronu- 
cleus with  that  of  the  sperm-cell  ;  for  this  end  the  latter  is 
exceedingly  minute  and  provided  with  a  vibratile  cilium  or 
"  tail,"  so  that  it  may  force  its  way  in  toward  the  centre 
of  the  egg.  These  sperm-cells  are  developed  in  the  testis 
of  the  male.  On  close  examination  with  very  high  powers  of 
the  microscope,  certain  cells,  called  "  mother  cells,"  maybe 
found  developed  in  fine  tubules  forming  the  gland  ;  these  are 
known  to  possess  several  nuclei,  which  are  destined  to  be- 
come spermatozoa  (Fig.  539,  a  and  V)  ;  these  multiply  until 
they  become  very  numerous,  elongated,  and  packed  side  by 


DEVELOPMENT  OF  ANIMALS.  645 

side  in  bun  dies  (e)  ;  f  rom  each  one  a  cilium  or  "tail  "  grows 
out,  when  they  are  set  free  from  the  mother-cell.  In  this 
tailed  form  they  are  very  active,  and  effect  the  fertilization 
of  the  egg  of  an  animal  of  the  same  species.  This  is  due  to 
contact  of  one  spermatozoon  with  the  female  pronucleus  situ- 
ated in  the  egg.  Immediately  after  the  spermatozoon  has 
penetrated  into  the  egg,  its  "head"  is  converted  into  a 
nucleus,  called  the  male  pronucleus  ;  after  this,  radiating 
stride  make  their  appearance  around  its  surface  ;  then  the 
male  pronucleus  travels  toward  the  female  pronucleus,  and 
finally  the  male  and  female  pronuclei  fuse  together  and  form 
the  first  "  segmentation  nucleus. " 

This  nucleus  subdivides,  and  the  result  is  a  mass  of  cells 
resembling  a  mulberry,  and  hence  called  the  morula.  The 
outer  circle  of  the  cells  of  the  morula  may  hereafter  form 
what  is  called  the  blastoderm  ;  after  a  while  it  pushes  in  at 
one  point,  and  the  portion  thus  forced  is  called  the  inner 
germ-layer  (endoderm)  and  the  outer  is  called  the  ectoderm 
or  outer  germ-layer,  and  in  this  condition  the  germ  is  called 
a  gastrula.  Subsequently,  a  third  layer  develops  from  the 
others — just  how  is  not  certainly  known — and  after  this  the 
different  tissues  become  developed. 

All  animals,  from  sponges  to  man,  become  first  two-  and 
afterward  three-layered  sacs  ;  so  that  all  animals  above  the 
Protozoa  not  only,  as  a  rule,  originate  from  eggs,  but  may  be 
said  to  travel,  up  to  a  certain  point,  the  same  developmental 
path.  From  this  point  the  members  of  different  types  of 
life  diverge.  How  different  are  the  modes  of  development 
of  animals  has  been  set  forth  in  the  different  life-histories 
related  in  the  foregoing  pages  of  this  book.*  But  the  laws 
of  growth  are  as  stable  and  uniform — certain  causes  pro- 
ducing certain  results — as  the  laws  of  the  motions  of  the 
heavenly  bodies. 

When  the  workings  of  these  laws  of  development  are  in- 
terfered with  by  sudden  accidents,  by  too  scanty  nourish- 
ment, and  by  the  transmission  of  the  effects  of  such  acci- 

*  For  a  fuller,  more  consecutive,  though  still  fragmentary  account, 
the  reader  is  referred  to  the  author's  "  Outlines  of  Comparative  Em- 
bryology, or  Life  Histories  of  Animals,  including  Man." 


646  ZOOLOGY. 

dents  or  abnormal  products  from  parents  who  have  been 
affected  by  them,  the  results  are  usually  abnormal,  more  or 
less  distorted  forms,  with  greater  or  less  defects  ;  and  here 
again  have  been  observed  laws  governing  the  production  of 
abnormalities,  the  study  of  these  being  called  teratology. 

We  may  study  the  mode  of  development  of  the  domestic 
fowl  or  hen  as  the  best  known  example  to  illustrate  the 
changes  undergone  by  an  embryo  vertebrate,  for  this  pur- 
pose condensing  the  statements  of  Foster  and  Balfour  in 
their  "  Elements  of  Embryology." 


Pig.  540.— Blastodermic  disk  and  germ  of  a  rabbit  about  one  day  old,  seen  from  the 
rack,  o,  edge  of  the  head-end  of  the  amni&n.;  ft,  fore-brain;  c,  lateral  expansion  of 
the  same,  or  primitive  eye-vesicle;  d,  middle,  e,  hind  brain.  There  are  eight  protover- 
tebne,  between  which  is  situated  the  spinal  cord.  Enlarged  ten  times.— After  Bischoff. 

First  Day. — After  fertilization  of  the  egg,  segmentation  of 
the  egg  occurs,  but  instead  of  being  total,  forming  a  morula 
or  mulberry  mass,  it  is,  as  in  all  birds  and  in  the  majority  of 
fishes  and  reptiles  (except  the  lanceletand  lamprey  eel),  par- 
tial, or  confined  to  the  periphery  of  the  yolk,  resulting  in 
the  formation  of  a  blastoderm,  the  oval  more  apparent  por- 
tion being  called  the  "  blastodermic  disk/'  which  is  the  be- 
ginning of  the  embryo.  In  six  or  eight  hours  after  fertili- 
zation the  three  germ-layers  appear.  From  the  outer  germ- 


DEVELOPMENT  OF  ANIMALS.  647 

layer  are  destined  to  arise  the  skin  and  wall  of  the  body 
with  the  nervous  system  ;  from  the  second  (mesoderm,  in 
the  embryo  called  the  mesoblast)  are  formed  the  heart  and 
the  vascular  system,  as  well  as  the  stomach  and  intestines. 

The  middle  layer  now  thickens,  causing  the  mark  known 
as  the  "  primitive  streak,"  along  the  middle  of  which  runs 
the  "  primitive  groove."  The  notochord  now  appears  and 
the  primitive  vertebrae  (protovertebrce,  Fig.  540).  The  am- 
nion  arises  as  a  membrane,  splitting  off  from  the  outer  germ- 
layer  of  the  embryo,  and  finally  forms  a  cavity  which  is 
filled  with  a  fluid.  About  this  time  the  allantois  arises  as 
an  offshoot  of  the  alimentary  canal,  budding  out  at  the 
hinder  end  of  the  embryo,  and  finally  curving  over  the  em- 
bryo, serving  as  a  foetal  respiratory  membrane. 

Second  Day. — The  three  portions  or  vesicles  of  the  brain 
now  appear  (Fig.  540),  as  well  as  the  alimentary  tract  and 
heart,  both  arising  in  the  head-fold  or  enlargement  (Fig.  540, 
a  to  c),  and  soon  the  blood-vessels  arise  as  channels  in  which 
blood -corpuscles  appear,  originating  as  amoeba-like  cells 
separating  from  the  cellular  mass  of  the  mesoderm.  Dur- 
ing the  second  day  also  the  eyes  and  ears  begin  their  devel- 
opment, being  at  first  simply  folds  or  inpushings  of  the 
outer  germ-layer. 

Third  Day. — This  is  one  of  the  most  eventful  days,  as  im- 
portant steps  in  the  elaboration  of  the  different  organs  are 
taken  ;  the  different  parts  of  the  brain,  of  the  alimentary 
tract  and  its  appendages  being  sketched  out,  and  the  rudi- 
ments of  the  lungs,  the  liver,  pancreas,  nose,  and  different 
parts  of  the  eye  and  ear  appearing.  On  the  fourth  day  the 
wings  and  legs  grow  out,  appearing  first  as  flattened  buds. 
The  notochord,  which  is  indicated  by  the  second  day,  by  the 
sixth  begins  to  diminish  in  size,  disappearing  by  the  time 
the  chick  is  hatched,  while  by  the  twelfth  day  the  deposition 
of  bone  in  the  bodies  of  the  vertebrae  commences.  Between 
the  eightieth  and  one  hundredth  hour  the  internal  differences 
in  the  sexes  appear,  the  testes  beginning  to  arise  on  the 
sixth  day. 

fifth  Day. — The  limbs  have  by  this  time  developed  so  as 
to  show  the  knee-  and  elbow-joints,  as  well  as  the  cartilages 


648 


ZOOLOGY. 


Fig.  541.— Five  schematic  figures  showing  the  development  of  the  foetal  egg-mem- 
branes,  where  in  all  except  the  last  the  embryo  is  represented  as  if  seen  in  longitudinal 
section.  1.  Diagram  of  egg  with  zona  pellucida,  blastoderm  (a,  i),  germinal  disk,  and) 
embryo.  2.  Egg  with  the  first  traces  of  the  yolk-sac  (d)  and  amnion  (ks,  ss,  and  am. 

3.  Egg  with  the  amnion  uniting  and  forming  a  sac  ;  the  allantois  (al)  budding  out. 

4.  Egg  with  the  villi  of  the  serous  membrane  (sz);  the  allantois  larger  ;  embryo  with 
mouth  and  anal  opening.    5.  Egg  in  which  the  vascular  layer  of  the  allantois  lies  close 
to  the  serous  layer  and  has  grown  into  the  villi  of  the  same,  constituting  the  true 
chorion  (cfi).   Yolk-sac  much  smaller,  about  to  be  drawn  into  the  cavity  of  the  amnion, 


DEVELOPMENT  OF  ANIMALS.  649 

which  precede  the  formation  of  the  bones  of  the  digits  and 
limbs.  The  primitive  skull  also  arises  from  the  mesoderm. 

Until  the  sixth  day  it  would  be  impossible  to  say  whether 
the  embryo  was  that  of  a  bird,  reptile,  or  mammal,  but  now 
the  characters  peculiar  to  birds  appear.  The  wings  and  legs 
manifest  their  bird-like  characters,  the  crop  and  intestinal 
cceca  are  indicated,  "  the  stomach  takes  the  form  of  a  giz- 
zard, and  the  nose  begins  to  develop  into  a  beak,  while  the 
incipient  bones  of  the  skull  arrange  themselves  after  the 
aviantype.  .  .  .  From  the  eleventh  day  onward,  the  embryo 
successively  puts  on  characters  which  are  not  only  avian, 
but  even  distinctive  of  the  genus,  species,  and  variety  " 
(Balfour).  By  the  ninth  or  tenth  day  the  feathers  originate 
in  sacs  in  the  skin,  while  the  nails  and  scales  begin  to  ap- 
pear on  the  thirteenth  day,  and  at  this  time  the  various 
muscles  of  the  body  can  be  distinguished.  Development  is 
thus  seen  to  be  from  the  general  to  the  special,  from  the 
simple  to  the  complex  ;  the  trunk  is  first  indicated  ;  while 
the  peripheral  parts — i.e.,  the  extremities,  the  digits,  the 
skin,  feathers  or  scales,  or  hair,  whatever  be  the  type  of 
Vertebrate — are  the  last  to  be  elaborated  ;  in  other  words, 
the  characters  of  the  branch,  class,  and  orders  are  the  first 
to  be  evolved,  those  of  the  family,  genus,  and  species  the 
last. 

The  development  of  the  rabbit,  guinea-pig,  or  any  mam- 
mal, including  even  man,  follows  much  the  same  order  as 
in  the  chick,  there  being,  however,  a  well-marked  morula  ; 
the  differences  are  due  to  the  fact  that  the  embryo  mammal 

d,  yolk-skin  ;  df,  villi  of  the  yolk-skin  ;  sh,  serous  membrane  ;  sz,  villi  of  the  serous 
membrane  ;  ch,  chorion  (vascular  layer  of  the  allantois);  chz,  true  villi  of  the  chorion 
(arising  from  the  projections  of  the  chorion  and  the  sac  of  the  serous  membrane); 
am,  amnion  ;  ks,  head-fold  of  the  amnion  ;  ss,  tail-fold  of  the  amnion  ;  ah,  cavity  of 
the  amnion ;  a,?,  sheath  of  the  amnion  for  the  navel-string  ;  a,  the  first  beginning  of 
the  embryo  arising  from  a  thickening  of  the  outer  layer  of  the  blastoderm  a' ;  m, 
thickening  forming  the  germ  in  the  middle  layer  of  the  blastoderm  (mO,  which  at  first 
only  reached  as  far  as  the  germinal  disk,  and  afterward  forms  the  vascular  layer  of 
the  yolk-sac  (df)  which  connects  with  the  intestino-muscular  layer  (darmf aserblatt) ; 
st,  sinus  terminates  ;  dd,  intestino-glandular  layer  (darmdrusenblatt)  arising  out  of  a 
part  of  i,  the  inner  layer  of  the  blastoderm  (afterward  the  epithelium  of  the  yolk- 
sac)  ;  kh,  cavity  of  the  blastoderm,  which-  afterward  becomes  (ds)  the  cavity  of  the 
yolk-sac  ;  dg,  passage  way  of  the  yolk ;  al,  allantois ;  e,  embryo ;  r,  original  space 
between  the  amnion  and  chorion,  filled  with  albuminous  fluid  ;  vl,  anterior  body-wall 
in  the  region  of  the  heart ;  hh,  cavity  of  the  heart  without  the  heart  itself.  In  Figs. 
2  and  3,  the  amnion  is,  for  the  sake  of  clearness,  represented  as  situated  too  far  away 
from  the  embryo  ;  so  also  the  cavity  of  the  heart  is  drawn  too  small  and  the  embryo 
too  large,  since,  except  in  Fig.  5,  they  are  only  drawn  diagrammatically.— From  Kol- 
liker's  "  Entwickelungsgeechichte  des  Menschen  und  der  hoheren  Thiere." 


650  ZOOLOGY. 

develops  in  a  specialized  portion  of  the  oviducts,  the  uterus 
or  womb,  and  that  the  growing  germ  until  birth  is  supplied 
not  with  yolk  as  food,  but  by  the  nourishment  in  the  ma- 
ternal blood.  In  fact,  while  the  eggs  of  reptiles  and  birds 
are  enormous,  it  was  not  known  with  certainty  until  1827 
that  mammals  developed  from  eggs.  The  eggs  of  these  an- 
imals are  very  minute,  owing  in  part  to  the  minute  amount 
of  yolk  they  contain  ;  that  of  man  being  less  than  a  quarter 
of  a  millimetre  (Tfa  inch)  in  diameter. 

The  mammalian  embryo,  nourished  as  it  is  through  the 
maternal  circulation,  needs  additional  temporary  organs  ; 
these  are  the  chorion  (Fig.  541,  ch),  formed  from  the  vitelline 
membrane  (present  in  birds  as  well  as  mammals),  which  sends 
off  villi  or  processes  extending  into  the  walls  of  the  womb. 
Besides  this,  in  the  higher  or  placental  mammals,  the  pla- 
centa or  after-birth  is  formed,  which  serves  as  an  organ  of 
respiration  as  well  as  to  supply  the  embryo  or  foetus  with 
nourishment,  and  to  carry  off  its  effete  products  by  means 
of  the  maternal  circulation. 

It  is  comparatively  late  in  embryonic  life  that  the  mam- 
malian features  appear  ;  in  the  dog  it  is  twenty-five  days 
before  it  can  be  told  whether  the  embryo  is  a  mammal  or 
not. 

All  mammals  may  be  said  to  pass  through  a  morula  and 
gastrula  stage.  In  the  next  stage  when  the  nervous  chord 
and  notochord  arise,  the  mammalian  germ  is  on  the  same 
footing  with  an  Ascidian  larva.  In  a  succeeding  stage, 
when  the  proto vertebrae  appear,  an  Amphioxus  stage  is 
reached ;  when  a  brain  is  formed,  the  level  of  the  fishes  is 
reached  ;  after  the  limbs  bud  out  the  young  mammals  may 
be  said  to  assume  the  condition  common  to  the  embryos  of 
all  Amphibian  and  higher  Vertebrates.  "When  the  allantois 
begins  to  appear  the  amphibian  feature  (the  want  of  an 
allantois)  is  dropped.  When  the  placenta  has  developed 
the  avian  characters  are  surpassed  and  the  mammalian  feat- 
ures assumed.  Thus  the  development  of  the  individual 
mammal  is  an  epitome  of  that  of  the  branch  or  type  to 
which  it  belongs,  and  the  successive  steps  in  the  degree  of 
specialization  of  the  individual  mammal  are  also  paralleled 


METAMORPHOSES  OF  ANIMALS.  651 

by  the  geological  succession  of  the  representatives  of  the 
different  classes,  as  without  much  doubt  lancelets  (or  at  least 
acraniate,  boneless  forms)  were  the  first  Vertebrates  to  ap- 
pear, and  we  know  that  fishes  appeared  before  Amphibians, 
that  their  type  culminated  before  the  reptiles  held  full 
sway  in  Mesozoic  times,  and  that  birds,  after  them  mam- 
mals, and,  last  of  all,  man  appeared,  who  crowns  the  series 
of  vertebrate  forms. 

Metamorphosis. — While  many  animals  are  hatched  like 
the  chick  with  the  form  of  the  parent,  others  pass  through 
a  series  of  changes  of  form  called  metamorphoses ;  these 
changes  of  form  adapt  the  animal  to  changes  in  its  sur- 
roundings, involving  alterations  in  its  mode  of  life — slight  if 
the  change  of  body-form  is  slight,  thorough-going  and  radi- 
cal if  its  body  becomes  profoundly  modified.  As  an  exam- 
ple of  a  complete  metamorphosis  may  be  cited  the  life-his- 
tories of  the  jelly-fishes,  the  star-fish,  sea-urchins,  sea-cu- 
cumbers, the  marine-worms,  the  mollusks,  the  crustaceans, 
insects,  and  the  salamanders  and  toads  and  frogs,  already  de- 
scribed in  the  foregoing  pages.  If  the  student  will  read  and 
compare  these  different  accounts,  and  then  consider  the 
striking  differences  between  the  complicated  histories  of  cer- 
tain species,  compared  with  the  direct  mode  of  growth  of 
other  species  of  the  same  order  or  family,  or  even  of  the 
same  genus,  the  inquiry  will  arise,  What  is  the  purpose  or 
use  of  such  a  series  of  changes  ?  If  he  look  carefully  into 
the  embryological  changes  of  those  species  which  are  born 
or  hatched  with  the  form  of  the  adult,  he  will  see  that  their 
embryological  history  is,  in  point  of  fact,  a  condensed  sum- 
mary of  the  changes  undergone  after  hatching  by  their  co- 
species,  which,  to  gain  the  same  adult  form,  have  been  sub- 
jected by  nature  to  a  series  of  complicated,  and,  at  first 
sight,  superfluous  changes  of  form  and  environment. 

Most  shrimps  and  crabs  undergo  a  complicated  metamor- 
phosis ;  in  the  different  changes  of  forms  they  lead  different 
lives,  and  are  subjected  to  different  surroundings,  the  larvae, 
for  the  most  part,  being  free-swimming  and  living  near  the 
surface  of  the  water,  while  the  parents  are  stationary.  The 
barnacle,  when  very  young,  swims  near  the  surface  of  the 


652  ZOOLOGY. 

sea,  afterward,  as  a  pupa,  becoming  fixed  to  a  rock  ;  the 
young  oyster-spat  swims  freely  about,  finally  becoming  fixed 
to  the  bottom.  This  change  of  life  and  of  form  undoubted- 
ly tends  to  prevent  the  extinction  of  the  species,  since,  if  at 
a  given  moment  the  parents  were  swept  out  of  existence, 
the  young  living  in  a  different  station  would  continue  to 
represent  the  species.  This  law  is  seen  to  hold  good  among 
insects,  where  many  species  are  represented  in  the  winter- 
time by  the  egg  alone,  others  by  the  caterpillars,  others  by  the 
chrysalis,  while  still  others  hybernate  as  imagines.  Again, 
in  the  marine  species,  the  free-swimming  young  are  borne 
about  by  ocean  and  tidal  currents,  and  in  this  way  what  in 
adult  life  are  the  most  sedentary  forms  become  widely  dis- 
tributed from  coast  to  coast  and  sea  to  sea.  On  the  other 
hand,  the  larval  forms  of  fixed  marine  animals  serve  as  food 
for  fishes,  especially  young  fishes  and  numerous  inverte- 
brates, while  their  stationary  parents  afford  subsistence  for 
still  other  forms  of  life  ;  thus  were  it  not  for  the  metamor- 
phoses of  animals,  many  species  would  become  extinct 
sooner  than  they  do,  while  the  great  overplus  of  larval 
forms  gives  to  many  other  species  of  animals  a  hold  on  ex- 
istence. 

Metamorphosis  among  the  invertebrate  animals,  espe- 
cially, is  perhaps  the  rule  and  not  the  exception.  Where  ani- 
mals develop  directly,  as  in  certain  insects,  crustaceans,  cer- 
tain salamanders,  toads  and  frogs,  this  is  due  to  some 
change  in  the  environment ;  in  the  case  of  Amphibians, 
perhaps  the  want  of  water,  or  some  other  cause,  there  always 
being  an  adaptation  in  the  case  of  the  direct  mode  of  de- 
velopment to  the  surroundings  of  the  animal  and  the  require- 
ments of  its  existence. 

Parthenogenesis,  and  Alternation  of  Generations.— 
Having  traced  the  normal  process  of  development  of  ani- 
mals, we  may  turn  to  certain  unusual  or  abnormal  modes  of 
production.  As  an  example  of  what  is  known  as  "  alternation 
of  generations,"  may  be  cited  the  mode  of  development  of  the 
jelly-fish,  such  as  the  naked-eyed  medusas  (Melicertum  and 
Campanularia),  which  at  one  time  of  life  develop  by  budding, 
at  another  by  eggs  ;  of  the  trematode  worms,  the  adult  forms 


ALTERNATION  OF  GENERATIONS.  65o 

of  which  lay  eggs,  while  the  redia  or  proscolex  of  the  same 
worm  produces  cercarice  by  internal  budding.  Here  also 
may  be  cited  the  cases  of  strobilation  of  the  Aurelia,  the 
tape-worm,  the  Nais,  Syllis,  and  Autolycus,  among  Anne- 
lids. Thus  among  Coelenterates  and  worms,  as  well  as  some 
Crustacea,  a  large  number  of  individuals  are  produced, 
not  from  eggs,  but  by  budding. 

Similar  occurrences  take  place  among  insects,  as  the 
Aphis  or  plant-louse,  in  which  a  virgin  Aphis  may  bring 
forth  in  one  season  nine  or  ten  generations  of  Aphides,  so 
that  one  Aphis  may  become  the  parent  of  millions  of 
young.  These  young  directly  develop  from  eggs  or  buds 
which  are  never  fertilized,  hence  the  term  parthenogenesis., 
or  virgin-reproduction,  sometimes  called  agamogenesis  (or 
birth  without  marriage).  The  bark-lice  as  well  as  the 
Aphides  develop  in  this  manner  during  the  warm  wea- 
ther ;  but  at  the  approach  of  cold  both  male  and  female 
Aphides  and  Coceidae  appear,  the  females  laying  fertilized 
eggs,  the  first  spring  brood  thus  being  produced  in  the 
normal,  usual  manner. 

Still  more  like  the  production  of  young  in  the  redia  of 
the  Trematode  worms  is  the  case  of  the  larva  of  a  small  gall- 
gnat  (Miastor),  which  during  the  colder  part  of  the  year  from 
autumn  to  spring  produces  a  series  of  successive  generations 
of  larvae  like  itself,  until  in  June  the  last  brood  develops 
into  sexually  mature  flies,  which  lay  fertilized  eggs. 

While  the  larval  Miaster  produces  young  like  itself,  the 
pupa  of  another  fly,  Chironomus,  also  lays  unfertilized  eggs. 

A  number  of  moths,  including  the  silk- worm  moth,  arc 
known  to  lay  unfertilized  eggs  which  produce  caterpillars. 
Among  the  Hymenoptera,  the  currant  saw-fly,  certain  gall- 
flies, several  species  of  ants,  wasps  (Polistes),  and  the  honey- 
bee, are  known  to  produce  fertile  young  from  unfertilized 
eggs  ;  in  the  case  of  the  ants  and  bees,  the  workers  lay  eggs 
which  result  in  the  production  of  males,  while  the  fertilized 
eggs  laid  by  the  female  ant  or  queen  bee  produce  females 
or  workers. 

Taking  all  these  cases  together,  parthenogenesis  is  seen  to 
be  due  to  budding,  or  cell-division,  or  multiplication.  Now, 


654  ZOOLOGY. 

it  will  be  remembered  that  the  egg  develops  into  an  animal 
by  cell-division,  so  that  fundamentally  parthenogenesis  is 
due  to  cell-division,  the  fundamental  mode  of  growth; 
hence,  normal  growth  and  parthenogenesis  are  but  extremes 
of  a  single  series.  In  this  connection,  it  will  be  remembered 
that  all  the  Protozoa  reproduce  by  simple  cell-division, 
that  among  them  the  sexes  are  not  differentiated,  that  they 
do  not  reproduce  by  fertilized  eggs  ;  hence,  so  to  speak, 
among  Protozoa  parthenogenesis  is  the  normal  mode  of  re- 
production ;  and  when  it  exists  in  higher  animals  it  may 
possibly  be  a  survival  of  the  usual  protozoan  means  of 
stocking  the  world  with  unicellular  organisms,  with  which 
we  know  the  waters  teem.  And  this  leads  us  to  the  teleol- 
ogy or  explanation  of  the  cause  why  parthenogenesis  has  sur- 
vived here  and  there  in  the  world  of  lower  organizations  ; 
it  is  plainly,  when  we  look  at  the  millions  of  Aphides,  of 
bark-lice,  the  hundreds  of  thousands  inmates  of  ant-hills 
and  bee-hives,  for  the  purpose  of  bringing  immediately 
into  existence  great  numbers  of  individuals,  thus  ensuring 
the  success  in  life  of  certain  species  exposed  to  great  vicis- 
situdes in  the  struggle  for  existence.  That  this  unusual 
mode  of  reproduction  is  all-important  for  the  maintenance 
of  the  existence  of  most  of  the  parasitic  worms,  is  abundantly 
proved  when  we  consider  the  strange  events  which  make  up 
the  sum  total  of  a  fluke  or  tape-worm's  biography.  With- 
out this  faculty  of  the  comparatively  sudden  production  of 
large  numbers  of  young  by  other  than  the  slow,  limited 
process  of  ovulation,  the  species  would  be  stricken  off  the 
roll  of  animal  life. 

Dimorphism  and  Polymorphism.— Involving  the  produc- 
tion of  young  among  many-celled  animals  (Metazoa)  by  what 
is  fundamentally  a  budding  process,  we  have  two  sorts  of 
individuals.  When  the  organism  is  high  or  specialized 
enough  to  lay  eggs  which  must  be  fertilized,  we  have  a 
differentiation  of  the  animal  into  two  sexes,  male  and  fe- 
male. Reproduction  by  budding  involves  the  differentia- 
tion of  the  animal  form  into  three  kinds  of  individuals — 
i.e.,  males,  females,  and  asexual  individuals,  among  insects 
often  called  workers  or  neuters.  These  have  usually,  as  in 


DIMORPHISM.  655 

ants  and  bees,  a  distinct  form  so  as  to  be  readily  recog- 
nized at  first  sight.  Among  the  Coelenterates  and  worms 
the  forms  reproducing  by  parthenogenesis  are  usually  larval 
or  immature,  as  if  they  were  prematurely  hurried  into  ex- 
istence, and  their  reproductive  organs  had  been  elaborated 
in  advance  of  other  systems  of  organs,  for  the  hasty,  sud- 
den production,  so  to  speak,  of  large  numbers  of  individu- 
als like  themselves. 

In  insects,  as  we  have  stated  elsewhere,*  dimorphism  is 
intimately  connected  with  agamic  reproduction.  Thus  the 
summer  wingless,  asexual  Aphis  and  the  perfect  winged 
autumnal  Aphis  may  be  called  dimorphic  forms.  The  per- 
fect female  may  assume  two  forms,  so  much  so  as  to  be  mis- 
taken for  two  distinct  species.  Thus,  an  oak  gall-fly  (Cy- 
nips  quercus-spongificd)  occurs  in  male  and  female  broods  in 
the  spring,  while  the  autumnal  brood  of  females  were  de- 
scribed originally  as  a  separate  species  under  the  name  C. 
aciculata.  Walsh  considered  the  two  sets  of  females  as  di- 
morphic forms,  and  that  Cynips  aciculata  lays  eggs  which 
produce  C.  quercus  spongifica.  Among  butterflies,  dimor- 
phism occurs.  Papilio  memnon  has  two  kinds  of  females, 
one  being  tailless,  like  the  tailless  male,  while  Papilio  Pam- 
mon  is  polymorphic,  there  being  three  kinds  of  females  be- 
sides the  male. 

There  are  also  four  forms  of  Papilio  Ajax,  the  three 
others  being  originally  described  as  distinct  species  under 
the  name  of  P.  Marcellus,  P.  Telamonides,  and  P.  WalsJiii. 
Our  Papilio  glaucus  is  now  known  to  be  a  dark,  dimorphic, 
climatic  form  of  the  common  Papilio  Turnus.  There  are 
dimorphic  males  among  certain  beetles,  as  in  the  Golofa 
hastata  Dejean,  of  Mexico,  in  which  one  set  of  males  are 
large  and  have  a  very  large  erect  horn  on  the  prothorax, 
and  in  the  other  the  body  is  much  smaller,  with  a  very 
short  conical  horn. 

Temperature  is  also  associated  with  the  production  of 
polymorphic  forms  in  the  temperate  regions  of  the  earth, 
as  seen  in  certain  butterflies,  southern  forms  being  varieties 

*  Guide  to  the  Study  of  Insects,  sixth  edition,  p.  52. 


656  ZOOLOGY. 

of  northern  forms,  and  alpine  "  species  "  proving  to  be  va- 
rieties or  seasonal  forms  of  lowland  species.  For  example, 
Weismann  states  that  the  European  butterflies,  Lycaon  amyn- 
tas  and  polysperchon,  are  respectively  summer  and  spring 
broods.  Anthocharis  Simplonica  is  an  alpine  winter  form  of 
Anthocharis  Bella,  as  is  Pieris  Iryonim  of  Pieris  napi.  In 
this  country,  as  Edwards  has  shown,  two  of  the  polymorphic 
forms  of  Papilio  Ajax — i.e.,  Walshii  and  Telamonides — come 
from  winter  chrysalids,  and  P.  marcellus  from  a  second 
brood  of  summer  chrysalids.  It  thus  appears  that  poly- 
morphism is  intimately  connected  with  the  origin  of  species. 
Perhaps  the  most  remarkable  case  of  polymorphism  is  to  be 
seen  in  the  white  ants  (Termites),  where  in  one  genus  there 
are  two  sorts  of  workers,  two  sorts  of  soldiers,  and  two  kinds 
of  males  and  females,,  making  eight  sorts  of  individuals  ;  in 
the  other  genera  there  are  six.  Among  true  ants  there  are, 
besides  the  ordinary  males,  females,  and  workers,  large- 
headed  workers.  In  the  honey-ant  (Myrmecocystus  Mexi- 
canus),  besides  the  usual  workers,  there  are  those  with 
enormous  abdomens  filled  with  honey.  Other  insects,  es- 
pecially certain  grasshoppers,  are  dimorphic.  Certain  par- 
asitic Nematode  worms  are  dimorphic  ;  and  among  the 
Ccelenterates,  especially  the  Hydroids,  there  is  a  strong  ten- 
dency to  polymorphism. 

Individuality.— Perfect  individuality  among  animals  is 
the  rule,  each  individual  being  capable  of  maintaining  an 
independent  existence  ;  but  we  have  seen  that  there  are  many 
of  the  lower  animals  in  which  it  is  difficult  to  determine 
whether  the  different  members  of  a  colony  are  really  in- 
dividuals or  simply  individualized  organs. 

The  student,  in  referring  back  to  the  account  of  the  Por- 
tuguese man-of-war,  will  find  it  difficult  to  say  whether  the 
four  kinds  of  members  of  the  floating  colony  are  organs  or 
individuals,  and  he  will  probably  agree  with  the  view  that 
it  is  best  to  provisionally  call  them  zooids  or  individualized 
organs  ;  for  the  feeders,  the  reproductive  zooids,  the  digest- 
ive zooids,  and  the  swimming  float,  or  the  swimming  bells 
of  the  other  Siphonophores,  are  highly  specialized  organs, 
and  only  differ  from  true  individuals  in  lacking  the  power 


INDIVIDUALITY  AND  HTBR1DITT.  657 

of  free  motion  and  of  maintaining  an  independent  existence. 
So  with  many  other  Coelenterates  and  with  the  tapeworm, 
whose  proglottides  or  segments  are  finally  capable  of  sepa- 
rate existence.  Among  the  higher  invertebrates,  even  the 
different  members  of  a  colony  of  white  or  true  ants  lack  a 
certain  amount  of  individuality,  the  workers  performing 
labors  upon  which  the  maintenance  of  the  very  existence  of 
the  colony  depends,  so  that  there  are  different  grades  of  in- 
dividuality, from  examples  like  the  Hydractinia  and  the 
Siphonophores  up  to  those  insects  which  live  socially  ;  and 
we  see  that  the  most  perfect  individuality  exists  in  those 
animals  which  can  most  efficiently  provide  for  their  own 
sustenance  and  for  the  continuance  of  their  species. 

Hybridity.— It  is  rare  that  two  species,  even  of  the  same 
genus,  can  produce  offspring  ;  when  such  cases  occur,  the 
result  is  called  a  hybrid.  For  example,  the  mule  is  a  hybrid, 
being  bred  from  a  female  horse  and  an  ass  ;  but  the  mule 
is  not  fertile,  and  hybrids  are  very  rarely  fertile.  The  In- 
dian dog  and  coyote  are  said  by  Coues  to  interbreed,  and 
on  the  Upper  Missouri  we  have  seen  dogs  which  had  every 
appearance  of  being  such  hybrids.  Dogs  also  cross  with  the 
fox  (Darwin).  The  American  bison  is  known  to  breed  with 
the  domestic  cattle,  and  it  seems  to  be  a  well-established 
fact  that  the  hybrids  are  fertile.  Fish  readily  hybridize. 

Darwin  states  that  he  knows  of  no  thoroughly  well-au- 
thenticated cases  of  perfectly  fertile  hybrid  animals,  though 
he  adds,  "  I  have  reason  to  believe  that  the  hybrids  from 
Cervulus  vaginalis  and  Reevesii  and  from  Phasianus  col- 
chicus  with  P.  torquatus  are  perfectly  fertile."  The  hare 
and  rabbit  are  supposed  to  have  fertile  offspring  ;  the  hy- 
brids of  the  common  and  Chinese  geese  (Anser  cygnoides) 
are  fertile.  The  crossed  offspring  from  the  Indian  humped 
and  common  cattle  interbreed.  Caton  has  hybridized  the 
Virginia  deer  with  the  Ceylon  deer  and  the  Acapulco  deer  ; 
"  the  hybrids  seem  perfectly  healthy  and  prolific."  Among 
insects  over  100  cases  of  hybridity  have  occurred,  but  it  is 
not  known  whether  the  offspring  are  fertile. 


CHAPTER  XI. 

THE    GEOGRAPHICAL    DISTRIBUTION     OF    ANI- 
MALS. 

THE  assemblage  of  animal  life  peopling  any  one  locality 
or  area  is  called  its  fauna,,  as  the  plants  of  a  place  consti- 
tute its  flora.  Where  the  physical  geography — i.e.,  the  con- 
tour of  the  surface,  the  plains,  valleys,  and  hills — is  of  iden- 
tical character  and  the  climate  the  same,  the  fauna  is  much 
the  same,  but  when  these  characteristics  of  soil  and  climate 
change,  as  in  passing  from  lowlands  to  highlands,  or  from 
south  to  north,  the  assemblage  of  animals  will  be  found 
to  change  in  a  corresponding  ratio.  And  as  there  are  no 
definite  limits  to  any  large  area  of  the  earth's  surface,  the 
physical  features  of  one  area  merging  insensibly,  as  a  rule, 
into  adjoining  districts,  so  adjoining  faunae  merge  into  one 
another,  and  a  certain  proportion  of  the  species  may  range 
through  two  or  more  faunal  areas. 

There  are  in  nature  causes  tending  to  restrain  animals 
within  their  faunal  limits,  and  others  tending  to  diffuse 
them,  or  to  cause  them  to  migrate  from  their  specific  cen- 
tres or  centres  of  creation — namely,  the  point  where  the  in- 
dividuals of  a  species  are  most  abundant,  and  where,  ac- 
cordingly, they  are  supposed  to  have  originated. 

Barriers  to  the  Spread  of  Animals  from  their  Specific 
Centres.— Among  the  most  important  are  the  oceans  and 
their  basins.  The  animals  of  the  opposite  sides  of  the  Pa- 
cific Ocean  are  entirely  unlike,  no  species  being  common  to 
the  two  sides  ;  while,  of  the  immense  numbers  of  animals 
peopling  the  coast  of  Brazil  and  the  opposite  coast  of  Af- 
rica, only  two  or  three  are  known  to  be  identical.  Differ- 
ence in  climate  is  also  a  great  barrier,  the  animals  of  the 


GEOGRAPHICAL  DISTRIBUTION.  659 

tropics,  as  a  whole,  being  unlike  those  of  the  temperate 
zones  ;  while  arctic  and  antarctic  animals  have  features  in 
common.  Mountains  serve  as  most  important  barriers,  re- 
straining animals  within  their  limits  ;  thus  the  basins  be- 
tween or  surrounded  by  continuous  ranges  of  mountains 
harbor  faunae  differing  from  those  on  the  opposite  sides  of 
the  mountains.  For  example,  the  majority  of  the  animals 
of  the  Great  Basin  between  the  Rocky  Mountains  and  the 
Sierra  Nevada  differ  from  those  of  the  Pacific  slope  or  the 
prairie  lands  lying  east  of  the  Rocky  Mountains,  as  the 
meteorological  and  geological  features  are  different.  The 
Cordilleras  of  South  America  form  a  barrier  to  the  diffusion 
westward  of  Brazilian  animals.  Still  this  fact  is  not  to  be 
taken  too  literally,  as  the  mountains  are  divided  by  valleys 
and  rivers,  which  afford  means  of  communication  and  an 
interchange  of  specific  forms  ;  thus  certain  species  of  ani- 
mals of  the  Rocky  Mountain  plateau  occur  on  each  side  of 
the  range,  as  do  those  in  the  Alleghany  district  of  the  At- 
lantic coast.  In  the  West  Indian  and  especially  the  Hawa- 
iian Islands,  where  the  species  of  land  snails  are  very  numer- 
ous, certain  forms  are  restricted  to  the  deep  narrow  valleys, 
being  confined  to  very  restricted  areas.  So  also  the  cold 
Alpine  summits  of  the  White  Mountains  of  New  Hamp- 
shire, of  the  Rocky  Mountains,  of  the  Alps  and  Scandina- 
vian mountains  harbor  a  few  species  either  peculiar  to  those 
extremely  limited  tracts  or  found  northward  in  the  Arctic 
regions. 

Deserts  may  act  much  as  inland  seas  to  separate  the  ani- 
mals of  the  adjoining  more  fertile  tracts,  and  they  afford 
dwelling-places  for  animals  which  are  incapable  of  living 
elsewhere.  Desert  faunas  have  a  general  fades  the  world 
over,  though  the  original  elements  out  of  which  the  faunae 
have  been  made  up  may  radically  differ. 

The  distribution  of  plants  also  has  much  to  do  with  that 
of  those  animals  which  are  dependent  on  them  for  food  ; 
as  a  rule,  the  distribution  of  both  plants  and  animals  de- 
pends on  the  same  physical  causes. 

Large  rivers  sometimes  act  as  barriers,  but  more  often, 
perhaps,  aid  in  the  diffusion  of  the  smaller  forms,  such  as 


060  ZOOLOGY. 

insects,  tnollusks,  and  crustaceans.  Different  systems  of  riv- 
ers have  distinct  sets  of  fluviatile  animals  ;  for  example,  the 
fishes  of  the  Ohio  and  Upper  Mississippi  and  its  tributaries 
differ  from  those  of  the  Hudson  River  and  the  New  England 
rivers,  and  the  latter  from  those  draining  the  Southern  At- 
lantic States.  The  fresh-water  mussels,  so  abundant  and 
characteristic  of  the  waters  of  the  Mississippi  and  its  tribu- 
taries are  confined  to  the  region  lying  west  of  the  Allegha- 
nies  and  east  of  the  Great  Plains.  The  fishes  and  mollusks 
of  the  rivers  of  the  Pacific  slope  differ  from  those  of  the 
scanty  waters  of  the  Great  Basin. 

Means  of  Dispersal.— The  most  general  are  the  alterna- 
tions of  winter  and  summer,  leading  birds  and  mammals  to 
migrate  great  distances  to  and  from  their  breeding-places. 
Ocean-currents  are  most  important  factors  in  the  dispersal 
of  many  marine  and  some  land  animals.  By  means  of  such 
great  currents  as  the  Gulf  Stream,  tropical  animals  are  borne 
to  temperate  and  even  subarctic  regions  ;  and,  on  the  other 
hand,  arctic  and  temperate  animals  are  borne  southward, 
and  thus  marine  faunae  interdigitate  and  merge  insensibly 
into  one  another.  By  this  agency  also  new  coral  islands 
are  peopled  from  the  mainland,  and  peninsulas  are  colo- 
nized from  adjoining  continents  or  islands  ;  for  example, 
the  southern  extremity  of  Florida  has  been  visited  by  trop- 
ical plants  and  animals  borne  by  currents  and  winds  from 
the  West  Indies,  thus  lending  a  purely  tropical  aspect  to 
the  southern  part,  a  semi-tropical  fauna  occupying  the  mid- 
dle and  northern  part  of  the  State. 

Trade  winds  play  an  important  part  in  scattering  insects, 
and  especially  the  minute  forms  of  life  ;  whirlwinds  and 
tornadoes  catch  up  larger  forms  and  transport  them  from 
stream  to  stream,  pond  to  pond,  and  from  lowlands  to 
highlands,  and  even  to  Alpine  summits,  where  may  some- 
times be  found,  under  loose  stones,  multitudes  of  insects 
which  have  been  borne  up  from  below  by  strong  gales  or 
ascending  currents  of  air. 

The  direction  of  the  migrations  of  the  Rocky  Mountain 
locust  seems  to  be  mainly  dependent  on  the  direction  of  pre- 
vailing winds.  Insects  as  well  as  birds  are  blown  off-shore 


GEOGRAPHICAL  DISTRIBUTION.  661 

sometimes  for  hundreds  of  miles,  and  in  this  apparently 
haphazard  way  islands  are,  in  part  at  least,  supplied  with 
their  quota  of  animal  life. 

Great  rivers,  like  the  Missouri,  Mississippi,  and  the  Ama- 
zons, afford  means  of  transportation  from  one  part  of  a  con- 
tinent to  another,  from  the  interior  to  the  seaboard,  of 
which  many  fishes,  insects,  and  especially  fluviatile  mollusks, 
avail  themselves.  Artificial  means  of  crossing  hroad  rivers 
are  offered,  to  insects  especially,  by  country-roads  and  bridges 
and  railroad  bridges,  of  which  the  potato-beetle  and  the 
cabbage-butterfly  have  fully  availed  themselves.  The  Colo- 
rado beetle  has  advanced  steadily  eastward,  suddenly  ap- 
pearing in  isolated  points  in  New  England,  having  appar- 
ently been  transported  by  through  grain-cars  from  Chicago, 
and  has  been  carried  to  Europe  in  vessels.  The  European 
cabbage-butterfly  introduced  into  Quebec  spread  southward 
into  Maine  along  the  Grand  Trunk  Railroad,  into  New 
York  along  the  railroads  from  Montreal  to  New  York,  and 
then  along  the  railroads  to  Washington. 

Geological  changes,  such  as  the  rise  and  submergence  of 
the  edges  of  continents,  and  also  the  incoming  and  wane  of 
the  glacial  period,  were  still  more  general  and  fundamental 
means  of  the  dispersal  and  rearrangement  of  faunae. 

Division  of  the  Earth  into  Faunae.— When  we  go  from 
Maine  to  California  we  shall  find  that  the  faunistic  features 
of  the  country  radically  change  three  times.  Leaving  the 
moist,  temperate,  forest-clad  Atlantic  region  with  its  char- 
acteristic animals,  and  entering  on  the  broad,  treeless,  dry, 
elevated  plateau  of  the  "Rocky  Mountains,  we  shall  notice 
that  the  Atlantic  fauna  has  been  replaced  almost  wholly  by 
a  new  and  strange  assemblage  ;  and  when  we  descend  the 
Pacific  slope  of  the  Sierra  Nevada,  there  will  be  found  to 
be  a  second  replacement,  though  much  less  marked  than 
the  first.  Again,  when  we  pass  from  Labrador  to  the  Isthmus 
of  Panama,  we  shall  find  several  distinct  faunae,  from  an 
arctic  one  to  a  purely  tropical  one.  If  we  pause  at  Wash- 
ington and  analyze  the  fauna  of  that  point,  we  shall  see 
that  it  is  made  up  mainly  of  animals  common  to  the  Middle 
Atlantic  States,  with  an  infusion  of  northern  and  southern 


662  ZOOLOGY. 

forms.  Indeed,  at  almost  any  point  in  temperate  North 
America  the  fauna  is  found  to  consist  of  three  elements — 
i.e.,  mainly  a  temperate,  with  a  certain  percentage  of  boreal 
or  subarctic  and  of  southern  or  semi-tropical  forms  ;  and  if 
the  point  be  situated  near  some  lofty  range  of  mountains,  a 
fourth  element — i.e.,  a  purely  arctic  or  alpine  feature — is 
superadded.  The  earth's  surface  may  then  be  mapped  out 
into  general  and  special  divisions.  First,  a  tropical,  tem- 
perate, and  arctic  or  circumpolar  fauna  or  realm,  and,  sec- 
ondly, each  continent  may  form  a  smaller  subdivision  or  spe- 
cific centre — i.e.,  the  Europeo- Asiatic,  the  African,  the  Aus- 
tralian, and  the  South  and  North  American  regions,  for 
each  of  these  continental  divisions  have  been  peopled  with 
animals  which  have  been  from  the  earliest  geological  times 
the  original  possessors  of  the  soil,  though  they  may  have 
adopted  members  of  each  other's  faunae. 

Confining  ourselves  to  the  North  American  Continent, 
let  us  examine  the  distribution  of  life  on  its  surface.  We 
shall  have  to  throw  out  the  arctic  regions,  which  belong 
with  the  arctic  regions  of  Europe  and  Asia,  to  a  distinct 
circumpolar  fauna  or  realm,  and  then  map  out  the  rest  of 
the  continent  into  five  provinces — i.e.,  the  Canadian,  the 
Alleghanian,  the  Central  or  Rocky  Mountains,  the  Pacific 
or  Oalifornian,  and  the  Mexican  ;  all  of  these  provinces  are 
bounded  by  natural  geological  limits  and  differ  in  tempera- 
ture and  moisture.  While  the  cougar,  or  Felis  concolor,  is 
common  to  each  one  of  them,  and  the  bison  and  black  bear 
range  throughout  the  Canadian,  Alleghanian,  and  Central 
provinces,  there  are  a  certain  percentage  of  animals  which 
are  confined  to  each  province  ;  and  on  closer  examination, 
each  province,  especially  on  the  Atlantic  and  Pacific  coasts, 
will  be  found  capable  of  minuter  subdivision  into  more  lo- 
cal faunae  or  faunulce.  • 

It  will  also  be  found  that  the  animals,  especially  the 
insects,  of  the  Atlantic  province  have  certain  elements 
reminding  us  of  Northeastern  Asia,  while  on  the  Pacific 
slope— i.e.,  the  Calif ornian  province,  a  few  insects,  shells, 
and  Crustacea,  as  well  as  the  birds,  remind  us  of  European 
types,  which  are  wholly  wanting  east  of  the  Rocky  Moun- 
tains. 


GEOGRAPHICAL  DISTRIBUTION.  663 

On  inquiring  into  the  origin  of  the  North  American 
fauna,  in  the  light  of  the  geological  history  of  the  conti- 
nent, we  shall  find,  first,  that  immediately  preceding  the 
glacial  period,  Arctic  America  was  peopled  by  a  flora  and 
fauna  of  which  the  larger  proportion  of  the  animals  of  the 
continent  north  of  latitude  30°  are  probably  the  descend- 
ants ;  and,  second,  that  a  number  of  species  migrated  north- 
ward from  the  South  American  Continent.  Now,  when 
the  glacial  period  came  in,  the  semi-tropical  and  warm  tem- 
perate animals  of  the  northern  two-thirds  of  the  continent 
were  mostly  swept  out  of  existence  ;  a  scanty  arctic  fauna 
took  their  place  ;  as  the  ice  melted  and  retreated  to  its  pres- 
ent limits,  the  present  assemblage  of  temperate  animals, 
mostly  modified  descendants  of  those  originally  driven  south, 
migrated  back  again  and  colonized  the  region  laid  compara- 
tively bare  by  the  ice  and  cold  of  the  glacial  period.  This 
is  an  illustration  of  the  sweeping  extinctions,  recolonizations, 
and  extended  migrations  of  animals  on  our  continent  in 
former  times,  by  which  the  existing  relations  of  faunae  have 
been  brought  about.  Parallel  events  have  occurred  on  the 
Europeo- Asiatic  Continent,  and  thus  geological  extinctions 
and  widespread  migrations  and  recolonizations  have  taken 
place  ;  and  it  is  only  in  this  way  that  the  existing  relations 
in  the  geographical  distribution  of  animals  as  well  as  plants 
can  be  accounted  for. 

It  should  also  bo  observed  that  in  the  beginning  of 
things  the  continents  were  built  up  from  north  to  south — 
such  has  been  at  least  the  history  of  the  North  and  South 
American  and  the  Europeo-Asiatic  and  African  Conti- 
nents ;  Jpd  thus  it  would  appear  that  north  of  the  equator, 
at  least,  animals  slowly  migrated  southward,  keeping  pace, 
as  it  were,  with  the  growth  and  southward  extension  of  the 
grand  land  masses  which  appeared  above  the^sea  in  the  Pa- 
leozoic Ages.  Hence,  scanty  as  is  the  arctic  and  temperate 
regions  of  the  earth  at  the  present  time,  in  former  ages  these 
regions  were  as  prolific  in  life  as  the  tropics  now' are,  the 
latter  regions,  now  so  vast,  having  all  through  the  Tertiary 
and  Quaternary  ages  been  undisturbed  by  great  geological 
revolutions,  and  meanwhile  been  colonized  by  emigrants 
driven  down  bv  the  incoming  cold  of  the  glacial  period. 


064  ZOOLOGY. 

It  appears,  then,  that  each  continent  has  had  from  the 
first  its  distinct  assemblage  of  life,  and  thus  opposing  con- 
tinents, such  as  South  America  and  Africa,  have  fundament- 
ally different  faunae,  because  they  have  had  a  separate  geo- 
logical history.  Though  the  climate,  moisture,  and  extent 
of  forests  of  Brazil  and  the  West  Coast  of  Africa  may,  for 
example,  be  nearly  identical,  the  animals  are  of  a  different 
type.  At  the  present  day,  Australian  trees  may  be  trans- 
planted to  California,  and  flourish  there,  and  camels  from 
the  Orient  may  breed  in  Southern  California,  because  at  the 
present  day  the  climate  and  soil  are  so  much  alike  in  the  two 
countries. 

Distribution  of  Marine  Animals.— Nearly  all  that  has 
been  said  thus  far  applies  to  land  animals.  Marine  species 
are  assorted  into  faunae  which  are  nearly  as  well  marked  as 
terrestrial  assemblages  of  species.  The  barriers  restraining 
them  within  their  faunal  limits  are  the  temperature  of  the 
water,  this  being  modified  more  or  less  by  the  ocean -cur- 
rents, the  nature  of  the  shore,  whether  rocky  or  muddy  or 
sandy,  and  the  nature  of  the  sea-bottom,  whether  also 
rocky,  muddy,  or  sandy.  Many  marine  animals  live  attached 
to  rocks  and  stationary  pebbles,  others  are  found  only  in 
coarse  or  in  fine  sand,  while  the  muddy  bottoms  of  harbors, 
bays,  and  gulfs,  or  the  soft,  deep  ooze  of  the  ocean-depths 
harbor  a  different  assemblage  of  mud-loving  species.  The 
temperature  of  the  water  is  the  most  important  agency  now 
in  operation  in  the  limitation  of  marine  animals.  Thus 
there  is  a  tropical,  north  and  south  temperate,  an  arctic 
and  probably  an  antarctic  zone,  and  these  are,  along  the 
shores  of  the  different  continents,  subdivided  int^Jtetinct 
faunae.  For  example,  along  the  coast  of  Eastern  North 
America,  the  arctic  or  circumpolar  fauna  extends  from  the 
polar  regions  to  Labrador  and  Newfoundland  ;  a  second, 
the  Acadian,  to  Cape  Cod  ;  between  Cape  Cod  and  Cape 
Hatteras  another  assemblage  (the  Virginian)  is 'found  ;  from 
Cape  Hatteras  to  Southern  Florida  a  fourth,  and  the  Flor- 
idan  peninsula  belongs  to  the  tropical  regions.  Along  these 
different  areas  the  water  is  of  different  temperatures.  We 
also  find  a  large  proportion  of  circumpolar  animals  in  the 


GEOGRAPHICAL  DISTRIBUTION.  665 

Acadian  fauna  and  a  few  in  the  Virginian  fauna,  as  the 
Labrador  or  polar  current  passes  down  along  the  coast, 
bathing  the  New  England  coast  north  of  Cape  Cod,  and 
even  extending  under  the  warm  surface-water  as  far  as  New 
Jersey.  On  the  other  hand,  the  great  volume  of  heated 
tropical  water  forming  the  Gulf  Stream  issuing  from  the 
Straits  of  Florida  makes  its  influence  most  sensibly  felt  as 
far  as  Cape  Hatteras,  and  in  a  diminished  degree  to  Cape 
Cod,  and  even  southern  shells,  etc.,  are  found  as  outliers  of 
more  southern  faunae  near  Portland,  Me.,  and  Nova  Scotia. 

As  we  descend  from  the  shore  into  deep  water,  the  tem- 
perature becomes  lower  and  lower  the  deeper  we  go,  until 
we  come  to  a  stratum  or  zone  of  water  about  32°-36°  Fahr., 
where  circumpolar  or  arctic  life  alone  abounds.  Wherever 
deep  abysses  off  the  coast  or  at  the  bottom  of  bays  or  gulfs 
occur,  the  water  is  found  to  be  colder  than  elsewhere  ;  just 
as  when  we  ascend  a  mountain  the  air  becomes  colder,  un- 
til at  the  Alpine  summits  we  find  an  arctic  temperature 
and  fauna  ;  thus,  in  the  sea,  increase  of  depth  is  paralleled 
by  increase  of  height  on  land. 

Usually,  off  the  coast  of  the  United  States,  north  of  New 
York,  there  is  a  distinct  zone  of  life  between  high  and  low 
water,  a  second  extending  to  the  depth  of  about  fifty  fathoms, 
and  a  third  to  one  hundred  fathoms  or  over.  At  a  depth  of 
from  one  or  two  hundred  fathoms  in  the  Northern  Atlantic, 
and  from  five  hundred  to  one  thousand  fathoms  in  the  sub- 
tropical and  tropical  seas,  down  to  the  deepest  parts  of  the 
ocean,  now  known  in  a  few  points  to  be  about  five  miles  in 
depth,  the  water  is  about  32°  Fahr.  and  the  animal  life  is 
pola^B  its  nature.  The  water  of  the  ocean  all  over  the 
globe,  as  shown  by  the  results  of  the  "  Challenger"  and 
other  expeditions  for  the  exploration  of  the  sea  at  great 
depths,  everywhere  below  a  depth  of  one  thousand  fathoms, 
is  of  an  arctic  temperature,  overlaid  by  the  heated  water  of 
the  tropics.*  The  abysses  or  deeper  parts  of  the  ocean-bed 
support  a  nearly  uniform  assemblage  of  life,  which  may  be 
called  the  deep-sea  or  abyssal  fauna.  The  animals  largely 
consist  of  Echinoderms,  notably  Crinoids,  with  Coelenterates, 
mollusks,  worms,  and  Crustacea,  and  it  is  an  interesting  fact 


666  ZOOLOGY. 

that  a  few  of  the  Echinoderms  belong  to  genera  which  flour- 
ished in  the  Cretaceous  Period  ;  so  that  in  a  sense  the  abys- 
sal fauna  may  be  said  to  be  an  extension  in  time  of  the 
Cretaceous  fauna  ;  the  physical  features  of  the  deeper  parts 
of  the  sea  having  remained  nearly  the  same,  while  the 
shallower  parts  have  risen  and  fallen  so  as  to  undergo  great 
changes,  and  have  wrought  corresponding  changes  in  the  life 
along  the  shores  of  the  continents. 

The  following  tabular  view  of  the  chief  zoological  faunas 
of  the  earth,  proposed  by  Mr.  J.  A.  Allen,  is  based  on  a 
study  of  the  mammals,  but  will  primarily  apply  to  most 
land  animals.  The  arctic  realm  is  most  distinctly  charac- 
terized by  the  distribution  of  marine  invertebrates,  when  it 
becomes  of  primary  value  : 

I.  Arctic  realm,  undivided. 

II.  North  Temperate  realm,  with  two  regions,  viz. : 

1.  American  region,  with  four  provinces,  viz.: 

a.  Boreal. 
6.  Eastern. 

c.  Middle.  * 

d.  Western. 

2.  Europseo-Asiatic  region,  also  with  four  provinces,  viz. : 

a.  European. 

b.  Siberian. 

c.  Mediterranean. 

d.  Manchurian. 

III.  American  Tropical  realm,  with  three  regions,  viz. :  flfc 

1.  Antillean. 

2.  Central  American. 

3.  Brazilian. 

IV.  Indo- African  realm,  with  two  regions,  viz. : 

1.  African  region,  with  three  provinces,  viz.  : 

a.  Eastern. 

b.  Western. 

c.  Southern. 


GEOGRAPHICAL  DISTHIB  UTION.  667 

2.  Indian  region,  with  two  provinces,  viz. : 

a.  Continental. 
6.  Insular. 

V.  South  American  Temperate  realm,  with  two  provinces,  viz. : 

a.  Andean. 

b.  Pampean. 

VI.  Australian  realm,  with  three  regions,  viz. : 

1.  Australian,  with  two  provinces,  viz. : 

a.  Australian. 

b.  Papuan. 

2.  Polynesian. 

3.  New  Zealand. 

VII.  Lemurian  realm,  undivided. 
VIII.  Antarctic  or  South  Circumpolar,  undivided. 

Migrations  of  Animals. — Intimately  connected  with  zoogeog- 
raphy are  the  migrations  of  animals,  especially  birds.  Nearly  all  the 
birds  of  the  United  States  which  breed  in  the  central  and  northern 
portions  pass  southward  in  the  autumn,  and  winter  in  the  Southern 
States  or  in  Central  America  and  the  West  Indies.  Most  of  the  birds 
which  breed  in  Northern  and  Central  Europe  fly  at  the  approach  of 
cold  weather  into  Southern  Europe  or  across  the  Mediterranean  into 
Northern  Africa.  The  causes  of  this  regular  periodical  migration  are 
probably  due,  primarily,  to  the  changes  of  the  seasons  and  to  the  want 
of  food  in  the  colder  portion  of  the  year,  and,  secondarily,  to  the 
breeding  habits  of  birds. 

The  periodical  migrations  of  fishes  from  deep  to  shoal  water  are 
connected  with  their  breeding  habits,  the  marine  fish  being  in  most 
cases  compelled  to  spawn  in  rivers  or  in  shoal-water.  The  migratory 
movements  of  fishes  along  the  coast  are  probably  connected  with  the 
presence  or  absence  of  their  accustomed  food. 

The  partial,  occasional  migrations  of  locusts  depend  on  the  undue 
increase  in  the  numbers  of  the  insects,  and  the  consequent  lack  of 
food,  while  the  direction  of  the  swarms  is  largely  dependent  on  the 
general  course  and  force  of  the  winds. 


CHAPTER  XII. 

THE  GEOLOGICAL  SUCCESSION  OF  ANIMALS. 

THE  different  systems  of  rocks,  from  the  Silurian  to  the 
Quaternary  or  present  age,  contain  the  fossil  remains  of  ani- 
mals, which  show  that  in  the  beginning  the  animals  were, 
as  a  whole,  unlike  those  now  living,  the  later  types  "becom- 
ing more  and  more  like  those  now  constituting  the  earth's 
fauna.  The  oldest  set  of  animals,  the  Palaeozoic,  comprised 
species  of  nearly  all  the  branches  of  invertebrates,  with  a 
few  fishes.  A  large  proportion  of  these  animals  belonged 
either  to  simple  or  to  what  are  called  generalized  types, 
though  some  were  as  specialized  as  any  invertebrates  now 
living.  Progress  upward  has  involved  the  disappearance  of 
most  of  the  generalized  types,  and  their  replacement  by  more 
or  less  highly  specialized  types.  Thus  the  earliest  corals  were 
mostly  of  the  Kugose  type,  which  were  succeeded  by  the 
more  complicated  recent  forms  ;  the  Brachiopods  or  shelled 
worms  were  replaced  by  mollusks  ;  the  generalized  trilobites 
gave  way  to  the  genuine  specialized  shrimps  and  crabs  ;  the 
existing  generalized  king-crab,  with  its  affinities  to  spiders, 
has  survived  a  number  of  still  more  generalized  or  synthetic 
allies.  The  generalized  sharks  and  ganoids  abounded  at  a 
time  when  there  were  no  bony  fishes  like  the  cod  and  her- 
ring. Nearly  nine  thousand  species  of  bony  fishes  have 
appeared  since  the  extinction  of  the  earlier- types  of  cartila- 
ginous and  mail-clad  fishes.  The  highly  specialized  horse 
was  preceded  by  a  number  of  more  generalized  species  and 
genera,  the  oldest  of  which  approached  the  tapir,  one  of  the 
most  generalized  of  mammals.  The  succession  of  forms 
leading  up  to  the  horse  is  paralleled  by  the  succession  of 


GEOLOGICAL    SUCCESSION  OF  ANIMALS.  669 

sea-urchins  and  of  ammonites,  the  older  being  of  simpler, 
more  generalized  forms,  and  the  later  with  a  greater 
specialization  or  elaboration  of  the  different,  especially  ex- 
ternal, hard  parts  of  the  body. 

"When  we  ascend  to  the  Amphibians,  the  reptiles  and  the 
mammals,  we  shall  find  that  there  has  been  an  elaboration 
or  working  out  into  great  detail,  of  the  parts  most  used  by 
the  animal,  this  differentiation  being  more  and  more  marked 
as  we  approach  the  present  time  ;  and  this  has  been  in  ac- 
cord with  the  building  up  of  the  continental  masses,  and 
the  differentiation  or  specialization  of  the  surface  of  the 
different  continents  into  plains,  plateaus,  highlands,  and 
mountain  ranges,  with  their  different  climatic  features, 
and  the  dividing  up  of  the  waters  into  mediterranean 
seas,  friths,  fiords,  rivers,  and  lakes.  Thus  the  extinction 
of  successive  faunae  all  over  the  globe  has  been  followed  by 
the  appearance  of  new  sets  of  animals,  each  assemblage  be- 
ing adapted  to  the  new  and  improved  condition  of  things. 

Having  seen  that  the  earlier  forms  of  life  were  of  a  sim- 
pler form,  though  often  combining  the  features  of  diverse 
classes  and  orders  of  animals  which  appeared  afterward,  so 
that  Agassiz  called  them,  in  some  cases,  prophetic  types, 
combining  as  they  did  characters  which  have  been  trans- 
mitted to  two  or  more  later  groups,  and  these  specially  elab- 
orated, so  that  such  generalized  or  prophetic  types  serve  as 
points  of  departure  from  which  several  series  of  forms  have 
arisen — having  traced  the  law  or  principle  underlying  the 
geological  succession  of  animals,  we  may  inquire  whether 
this  has  been  paralleled  by  the  development  of  any  one  of 
the  members  of  a  group.  That  this  is  the  case  has  been 
proved  by  Hyatt,  who  shows  that  the  development  of  the 
individual  Ammonite  is  paralleled  by  that  of  the  geological 
succession  of  the  members  of  the  order  to  which  it  belongs. 
Stalked  Crinoids  were  the  style  in  Palaeozoic  ages,  while  free 
Crinoids  are  more  abundant  at  the  present  day  ;  and  we 
have  seen  that  in  the  individual  development  of  the  existing 
Antedon,  the  young  is  stalked  at  first,  afterward  becoming 
free.  The  young,  bony  fish  has  at  first  a  cartilaginous 
skeleton  and  a  heterocercal  tail,  these  being  characteristics 


670  ZOOLOGY. 

of  early  fishes.  The  earlier  Batrachians  were  tailed,  the 
tailless  toads  and  frogs  in  general  appearing  last,  as  the 
tadpole  precedes  the  frog  condition. 

Extinction  of  Species.— The  laws  governing  the  extinction 
of  animals  are  obscure,  but  we  know  that  geological  extinc- 
tions must  have  been  due  to  natural  causes,  since  the  earth 
has  at  different  periods  evidently  undergone  great  changes, 
sufficient  to  account  for  the  death  of  such  species  as  were 
unable  to  withstand  the  oscillations  and  changes  of  climate. 
In  Palaeozoic  times  existed  multitudes  of  animals  which,  judg- 
ing by  their  descendants  of  later  times,  belonged  to  old-fash- 
ioned, obsolete,  useless  types.  They  cumbered  the  ground, 
and  were  destroyed  by  the  beneficent  action  of  unerring  natu- 
ral laws  promoting  the  decay  and  extinction  of  antiquated 
forms,  and  the  recreation,  by  the  laws  of  transmission  with 
modification,  of  new,  improved  types,  useful  in  their  day  and 
generation  as  stepping-stones  to  a  still  higher,  more  improved 
stock.  That  the  extinction  was  due  to  causes  acting  pri- 
marily from  without,  and  secondarily  from  within  by  trans- 
mission force,  seems  demonstrated  when  we  take  into  ac- 
count the  destruction  of  life  which  we  know  took  place 
during  and  at  the  close  of  the  Glacial  Period,  when  the 
earth  was  swept  with  glaciers,  and  afterward  garnished 
with  the  vegetation  and  fresh  life  of  the  post-glacial  times, 
and  made  ready  for  the  abode  of  man.  Thus  the  death  of 
species  by  the  action  of  laws  that  we  can  comprehend  in- 
volves the  recreation  of  new  and  improved  animal  forms  by 
laws  that  we  can  at  least  in  part,  if  not  fully,  understand. 


CHAPTER  XIII. 

THE   OKIGIN   OF   SPECIES. 

THE  extinction  of  species  was  in  some  cases  gradual,  in 
others  sudden,  so  in  all  probability  as  different  assemblages 
of  life  became  slowly  extinct  new  forms  as  slowly  originated 
from  them  by  genetic  descent  and  took  their  places.  While 
here  and  there  certain  species,  under  favorable  circumstances, 
suddenly  appeared,  if  we  could  have  been  there  to  look  on, 
it  would  perhaps  have  been  as  difficult  to  have  observed  the 
process  as  it  is  at  the  present  day  to  observe  the  changes 
going  on  in  the  relation  of  existing  faunae.  We  know, 
however,  that  changes  are  going  on  in  the  world  of  life  about 
us,  that  the  balance  of  nature  is  being  disturbed. 

The  nature  of  the  evidence  tending  to  prove  that  species 
have  originated  through  the  agency  of  physical  and  biologi- 
cal laws  is  mainly  circumstantial,  there  being  comparatively 
few  facts  in  demonstration  of  the  theory,  the  direct  act  of 
transformation  of  one  species  into  another  under  the  eye  of 
scientific  experts  having  never  been  observed. 

Reasoning  d  priori,  we  assume  that  organisms,  both 
plant  and  animal,  have  been  created  by  development  from 
pre-existent  forms  because  it  agrees  with  the  general  course 
of  nature.  All  the  events  in  geology,  as  in  physics  and  as- 
tronomy, being  due  to  the  operation  of  natural  laws,  it  is 
reasonably  supposed  that  the  production  of  all  the  species 
of  plants  and  animals  from  original  simple  forms,  like  the 
Monera  or  bacteria,  have  been  the  result  of  the  action  of 
natural  law.  The  study  of  the  early  forms  of  life  found  in 
the  Palaeozoic  strata  ;  the  laws  of  the  succession  of  types  ;  the 
correlation  existing  between  the  development  of  the  indi- 


672  ZOOLOGY. 

vidual  and  of  the  members  of  the  class  to  which  it  belongs  ; 
the  parallelism  between  the  formation  and  differentiation 
of  the  land-masses  of  the  globe  and  the  successive  extinc- 
tions and  creations  of  plants  and  animals — all  these  facts, 
notwithstanding  the  imperfections  of  the  geological  record, 
and  the  fact  that  many  of  the  older  forms  of  animals  were 
nearly  as  much  specialized  as  those  now  living  ;  tend  strongly 
to  prove  that,  on  the  whole,  the  world  as  it  now  exists  has 
been  the  result  of  progressive  development,  one  form  com- 
ing genetically  from  another  ;  the  animal  and  plant  worlds 
constituting  two  systems  of  blood  relations,  rather  than  sets 
of  independent  creations. 

When  to  more  special  studies  of  those  species  which  live 
in  extraordinary  environments,  such  as  cave- animals,  para- 
sitic animals,  brine-inhabiting  animals,  Alpine  forms  and 
certain  deep-sea  species,  we  add  the  study  of  rudimentary 
organs  in  adult  animals,  of  temporary,  deciduous  organs  in 
young  or  larval  animals  ;  when  we  compare  the  metamor- 
phoses of  some  species  congeneric  with  others  which  undergo 
no  transformations  ;  when  we  study  the  delicate  balance  in 
nature  as  observed  in  the  geographical  distribution  of  ani- 
mals ;  the  harmony  in  nature  between  species  and  their  en- 
vironment ;  protective  coloration  and  resemblance  in  form, 
the  relations  between  carnivorous  and  herbivorous  creatures, 
the  struggle  for  existence  between  animals,  we  are  forced 
to  acknowledge  that  the  operations  of  nature,  as  a  whole, 
tend,  on  the  one  hand,  to  the  origination  of  new  forms 
and  the  preservation  of  those  which  are  useful,  or,  in  other 
words,  are  in  harmony  with  their  surroundings  ;  and,  on  the 
other  hand,  to  the  destruction  of  those  which  are  incapaci- 
tated by  changes  in  their  environment  for  existence  in  what 
has  been  and  now  is  a  constantly  changing,  progressive 
world. 

Again,  reasoning  by  induction,  as  an  actual  fact  we  know 
that  species  vary  ;  that  hardly  any  two  experts  agree  exactly 
as  to  the  limitation  of  species  ;*  that  varieties  tend  to  break 

*  As  one  of  many  examples,  we  may  cite  the  fact  that  fifty-nine  nom- 
inal species  of  the  squirrels  have  been  described  as  inhabiting  tropical 
America,  but  lately  the  number  has  been  reduced  to  twelve. 


THE  ORIGIN  OF  SPECIES.  673 

up  into  races,  and  that  no  two  individuals  of  a  race  are  ex- 
actly alike.  Where  the  climate  and  soil  remain  the  same, 
the  species  tends  to  remain  fixed  and  stable  ;  remove  the 
stability  in  the  environment,  or  subject  the  individuals  of  a 
species  to  changes  of  soil  and  temperature,  and  expose  it 
more  than  usual  to  the  attacks  of  its  natural  enemies,  it 
then  begins  to  undergo  a  change.  This  is  seen  in  those  in- 
dividuals of  a  species  which  live  on  the  borders  of  lowlands 
and  highlands,  of  deserts  and  fertile  tracts,  of  salt  and 
brackish  water,  of  shallow  and  deep  water,  and  of  polar  and 
temperate  zones,  or  to  the  influence  of  alternating  cold  and 
warm  weather.  When,  as  in  some  cases,  climatic  or  other 
agencies  suddenly  change,  we  may  have  species  and  even 
genera  suddenly  appearing,  as  is  known  to  be  the  case  in 
the  change  of  one  genus  to  another  of  brine  shrimps  when 
the  water  changes  from  brackish  to  a  brine,  as  worked  out 
by  Schmankevitch  in  Russia. 

The  struggle  for  existence  resulting  in  the  survival  of  the 
fittest  is  a  fact  now  generally  observed.  The  cod  may  de- 
posit several  millions  of  eggs,  but  of  this  immense  number 
only  one  or  a  few  pair  of  adults  survive  ;  there  are  probably 
no  more  codfish  now  than  two  centuries  since — indeed,  not 
as  many  ;  the  eggs  are  devoured  by  different  animals,  the 
young  fish,  as  soon  as  hatched,  form  the  food  of  larger  fish, 
half -grown  cod  serve  to  supply  the  wants  of  larger  animals, 
until  finally  the  survivors  may  be  to  the  original  number  of 
eggs  as  one  to  a  million.  The  queen  bee  may,  during  her 
whole  life,  lay  more  than  a  million  of  eggs,  the  queen 
white  ant  may  lay  eighty  thousand  eggs  a  day,  an  Aphis 
may  be  the  mother  of  a  hundred  young,  those  hundred  may 
each  produce  their  centesimal  offspring  until  the  result  in  one 
season,  at  the  end  of  the  tenth  generation,  amounts  to  a 
quintillion  of  plant-lice  ;  but  most  of  these  insects  serve  as 
food  for  other  species,  many  die  of  disease  and  cold,  until 
at  the  end  of  the  season  only  one  or  several  pairs  survive  to 
lay  a  few  eggs,  which  represent  the  species  in  the  winter-time. 

Lastly,  the  variation  in  domestic  animals,  the  result  of 
the  subjection  of  the  species  to  influences  not  felt  in  what 
we  call  a  state  of  nature,  is  an  indication  that  animals  not 


674  ZOOLOGY.  9 

exposed  to  human  interference  may  vary  when  subjected  to 
changes  in  their  environment.  Also  the  fact  that  man  can,  by 
careful  selection,  breed  races  of  horses  adapted  for  draught, 
speed,  or  the  road  ;  races  of  cows  for  different  qualities  of 
milk  ;  beeves  for  meat ;  races  of  sheep  for  pre-eminence  in 
the  quality  of  their  wool  or  mutton,  or  races  of  doves  or 
poultry  for  beauty,  usefulness,  or  other  qualities  ;  the  fact 
that  gentleness,  and  generally  good  mental  qualities,  can  be 
made  to  replace  viciousness  in  horses,  cattle,  dogs — all  these 
and  many  other  facts,  in  the  art  of  breeding  animals  known 
to  fanciers,  indicate  that  nature  has,  through  the  past  ages, 
by  the  operation  of  natural  laws,  evolved  races  and  species 
of  animals  which  have  followed  constantly  improving  lines 
of  development,  the  outcome  of  which  are  creatures  the  best 
fitted  to  withstand  the  struggle  for  existence,  the  most  use- 
ful in  the  scheme  of  nature,  and  the  most  in  harmony  with 
the  world  about  them.  Progress,  on  the  whole,  therefore, 
has  been  beneficent,  the  best  proof  of  which  is  the  last 
product  of  evolution,  man,  the  paragon  of  creation. 


CHAPTER  XIV. 

•      PROTECTIVE  RESEMBLANCE. 

CLOSELY  related  to  the  foregoing  subjects  is  the  protective 
resemblance  or  "  mimicry"  of  natural  objects  by  which  spe- 
cies of  animals  are  preserved  from  extinction.  Animals  may 
"  mimic"  or  imitate,  or  be  assimilated  in  shape  or  in  color 
to  natural  objects,  as  stones,  lichens,  dry  bushes,  the  bark 
of  trees,  or  portions  of  leaves,  or  entire  leaves,  fresh  or 
dried,  and  their  stems,  or  so  closely  imitate  other  animals 
which  enjoy  an  immunity  from  attack  as  to  escape  notice 
or  attacks  from  their  enemies,  and  thus  prolong  their  own 
lives  and  that  of  their  species. 

The  animal  is,  as  a  rule,  unconscious  that  it  is  thus  pro- 
tected ;  though  there  are  examples,  as  in  the  case  of  the 
trap-door  and  other  spiders,  which  cover  their  holes  in  such 
a  way  to  avoid  notice  that  it  would  appear  as  if  they  were 
semi-conscious  or  aware  of  what  they  were  doing. 

In  the  first  place,  we  know  that  animals  may  be  deceived, 
as  is  proved  by  the  various  subterfuges  employed  by  hunters 
in  tolling  or  deceiving  the  larger  indrupeds,  the  use  of 
decoy-ducks,  by  which  water-fowl  are  oi^en  thoroughly  de- 
ceived and  brought  within  reach  of 'the  gun. 

The  disguises  worn  by  animals,  the  exquisite  adaptation 
of  the  colors  of  their  fur  or  feathers  to  their  surroundings, 
are  part  of  the  general  harmony  existing  throughout  nature. 
Desert  animals  are  rusty  or  light-colored  ;  birds  and  insects 
and  lizards,  as  well  as  frogs  and  tree-toads,  which  live  among 
trees,  are  green  ;  those  which  live  among  the  trunks  and 
larger  branches  of  trees  assimilate  in  color  to  the  color  of 
the  bark.  The  cougar,  which  clings  to  the  trunk  of  some 


676  ZOOLOGY. 

tree,  prepared  to  spring  upon  the  deer  passing  underneath, 
is  protected  from  observation  by  its  brown  neutral  color, 
while  the  bars  and  lines  of  the  tiger  are  said  to  resemble  the 
lights  and  shades  of  the  jungle  grass  in  which  it  lies  in  wait 
for  its  prey.  The-  prairie-dog,  the  deer,  buffalo  and  ante- 
lope on  the  Western  plains,  are  concealed  by  their  resem- 
blance in  color  to  the  soil,  or  to  the  bushes  on  its  surface. 

Among  insects,  the  grasshoppers  nearly  always  harmonize 
in  color  with  the  general,  hue  of  the  fields  in  which  they 
abound  ;  insects  on  light-colored  sandy  beaches  are  often 
pale,  as  if  bleached  out  by  the  sun's  rays.  Alpine  and  arctic 
butterflies  and  moths,  which  have  limited  powers  of  flight, 
when  nestling  on  lichen-covered  rocks,  are  difficult  to  detect. 


Fig.  542.— A  Katydid-like  form  resembling  a  leaf. 

Certain  orthopterous  insects  resemble  leaves  ;  such  are 
certain  katydids  (Fig.  542),  and  especially  the  famous  leaf- 
insect,  Phyllium  siccifolium  Linn.  (Fig.  543),  which  strik- 
ingly resembles  a  green  leaf.  The  stick-insects  (Fig.  544) 
also  would  be  easily  mistaken  for  the  twigs  of  trees  or  stalks 
of  leaves,  one  species  (Fig.  544)  representing  a  moss-grown 
twig.  The  under  sides  of  the  wings  of  our  native  Grapta 
butterflies  have  the  color  of  dead  leaves,  so  that  when  they 
are  at  rest  they  resemble  a  withered  dry  leaf.  The  most 
perfect  resemblance  to  a  leaf  with  its  stem  is  the  Xallima 
butterfly  when  setting  at  rest  with  its  wings  folded  over  its 


PROTECTIVE  RESEMBLANCE. 


677 


Fig.  543.— Leaf  insect  (Phy- 
um).    Half  natural  size. 


back.     The  caterpillars  of  the  geometrid  moths  often  won- 
derfully mimic  the  stems  of  the  plants  they  feed  upon,  in 
color   and   markings,    even    to    the 
warts  and  tubercles  on  their  skin. 

As  an  example  of  possibly  con- 
scious mimicry  or  effort  at  conceal- 
ing their  nest  from  the  search  of 
their  enemies,  may  be  cited  the  trap- 
door spider  observed  by  Moggridge 
in  Southern  Europe.  This  spider 
digs  its  hole  among  moss  and  small 
ferns,  and  after  the  trap-door  is 
made  the  top  is  covered  with  growing 
ferns,  etc. ,  transplanted  by  the  spider, 
and  the  deception  is  so  perfect  that 

Mr.  Moggridge  found  it  difficult  to  detect  the  position  of 
the  closed  trap,  even  when  holding  it  in  his  hand. 

Mimicry  of  other  insects  is  of 
very  frequent  occurrence,  certain 
flies  resembling  bees  in  appearance 
and  the  sounds  or  buzzing  they 
make  ;  the  Syrphus  flies  closely 
imitate  wasps.  Fig.  545  illustrates 
a  case  observed  by  Belt  in  Nicara- 
gua, where  a  wasp  (Priocnemis)  is 
mimicked  by  a  hemipterous  insect 
(Spiniyer  luteocornis  Walker,  the 
left-hand  figure)  in  every  part, 
even  to  its  vibrating,  brown,  semi- 
transparent  wings  and  its  wasp-like 
motions.  Here  the  bug  is  evidently 
protected  by  its  resemblance  to  the 
wasp,  for  whose  ferocity  and  sharp 
sting  all  unarmed  insects  have 
great  respect. 

Some  butterflies  are  distasteful 
to  birds,  and  there  are  other  but- 
terflies which  have  no  bad  taste,  but  closely  resemble  in 
color  such   species   as   are   passed   over  by   birds.     Thus, 


Fig.  544.— Stick  insect. 


678  ZOOLOGY. 

Danais  archippus,  a  common  large  butterfly,  is  not  eaten 
by  birds  on  account  of  its  pungent  odor,  which  is  disagree- 
able to  them.  Another  butterfly,  Limenitis  disippus,  a 
smaller  but  similarly  colored  butterfly,  which  is  inodorous, 
is  supposed  to  be  mistaken  by  the  birds  for  the  Danais,  and 
thus  escapes  destruction. 

Belt  says  that  in  Central  America  stinging  ants  are  not 
only  closely  copied  in  form  and  movements  by  spiders,  but 
by  species  of  Hemiptera  and  Coleoptera ;  as  stinging  ants 
are  not  usually  eaten  by  birds,  this  disguise  is  thought  to 
protect  the  various  forms  which  imitate  them. 

Many  highly-colored  caterpillars,  which  live  exposed  on 
the  leaves  of  plants,  are  not  eaten  by  birds,  owing  to  their 
bad  taste.  This  and  other  bright-colored  insects  may  be  said 


Fig.  545.— Wasp  mimicked  by  a  bug.— After  Belt, 

to  hang  out  danger-signals  to  warn  off  hungry  birds.  Mr. 
Belt,  in  his  "  Naturalist  in  Nicaragua,"  suggests  that  the 
skunk  is  an  example  of  this  kind.  "  Its  white  tail,  laid 
back  on  its  black  body,  makes  it  very  conspicuous  in  the 
dusk  when  it  roams  about,  so  that  it  is  not  likely  to  be 
pounced  upon  by  any  of  the  Carnivora  mistaking  it  for  other 
night-roaming  animals."  He  also  cites  the  case  of  a  very 
poisonous,  beautifully  banded  coral  snake  (Elaps),  which  is 
"  marked  as  conspicuously  as  any  noxious  caterpillar  with 
bright  bands  of  black,  yellow,  and  red."  This  author  also 
found  that  while  the  frogs  in  Nicaragua  are  dull  or  green- 
colored,  feeding  at  night,  and  all  preyed  upon  by  snakes 
and  birds,  one  little  species  of  frog,  dressed  in  a  bright  liv- 


PROTECTIVE  RESEMBLANCE. 

ery  of  red  and  blue,  hops  about  in  the  day-time,  and,  as  lie 
proved  by  experiment,  is  thoroughly  distasteful  to  fowls 
and  ducks. 

We  have  seen  that  many  animals  resemble  externally  those 
above  them  in  the  scale  of  life  ;  in  the  synthetic  or  general- 
ized types  from  which  the  more  specialized  forms  have  prob- 
ably originated,  there  are  characters  which  cause  them  to 
resemble  more  recent,  new-fashioned  types.  It  is  possible 
that  in  many  cases  the  older  types,  doomed  as  they  were  to 
destruction,  have  had  their  existence  prolonged  by  their 
protective  resemblance  to  modern  types. 

For  example,  the  Neuroptera  as  a  group  are  geologically 
of  high  antiquity  ;  owing  to  geological  extinction,  but  few 
species,  compared  with  those  of  other  orders,  have  survived  ; 
and  those  which  are  now  living  often  resemble  members  of 
higher,  more  recent  orders.  The  inference  is,  then,  that 
the  mimickers  have  survived  by  reason  of  their  resemblance 
to  the  more  abundant  forms  which  appeared,  as  the  more 
old-fashioned  types  were  waning  or  dying  out. 

Certain  Brazilian  species  of  the  lepidopterous  family, 
Zygcenidce  and  Bombycid&,  mimic  in  form  and  coloration 
certain  butterflies,  especially  the  ffeliconidce,  which  abound 
in  Brazil.  The  former  groups  are  evidently  the  older  geo- 
logically, as  there  are  wide  gaps  between  the  genera ;  and 
the  indications  are  that  these  butterfly-like  moths  have 
likewise,  from  their  resemblance  to  the  more  abundant  Heli- 
conidce,  been  preserved.  It  thus  appears  that  protective 
mimicry  may  be  an  important  factor  in  the  preservation  of 
species. 


CHAPTER  XV. 

INSTINCT  AND  EEASON  IN  ANIMALS. 

WE  have  seen  that  animals  have  organs  of  sense,  of  per- 
ception, in  many  cases  nearly  as  highly  developed  as  in  man, 
and  that  in  the  mammalia  the  eyes,  ears,  organs  of  smell 
and  touch  differ  but  slightly  from  those  of  our  own  species  ; 
also  that  the  brain  and  nervous  system  of  the  higher  mam- 
mals closely  approximate  to  those  of  man.  We  know  that 
all  animals  are  endowed  with  sufficient  intelligence  to  meet 
the  ordinary  exigencies  of  life,  and  that  some  insects,  birds, 
and  mammals  are  able,  on  occasion,  to  meet  extraordinary 
emergencies — in  other  words,  to  rise  with  the  occasion. 
These  occurrences  indicate  that  what  usually  goes  by  the 
name  of  "  instinct "  is  more  or  less  pliable,  unstable  ; 
that  animals  are  in  a  limited  degree  free  agents,  with  powers 
of  choice.  Moreover,  those  naturalists  who  observe  most 
closely  and  patiently  the  habits  of  animals  do  not  hesitate 
to  state  their  belief  that  animals,  and  some  more  than 
others,  possess  reasoning  powers  which  differ  in  degree 
rather  than  in  kind  from  the  purely  intellectual  acts  of 
man. 

As  a  matter  of  not  infrequent  observation,  animals  exer- 
cise the  power  of  choice,  they  select  this  or  that  kind  of 
food,  prefer  this  or  that  kind  of  odor,  and  have  their  likes 
and  dislikes  to  certain  persons,  and  all  this  aside  from  mere 
physical  stimulation  of  the  senses.  Moreover,  animals  are 
subject  to  the  passions,  they  show  anger,  even  when  not 
hungry  or  under  the  domination  of  the  reproductive  in- 
stincts ;  their  sounds  express  dissatisfaction  or  contentment. 
Indeed,  many  facts  could  be  stated  showing  that  animals 


INSTINCT  AND  REASON.  681 

not  only  have  feelings,  intelligence,  and  volition,  but  are 
possibly,  in  a  very  slight  degree,  self-conscious.  The  fact 
that  animals  exercise  discrimination  in  the  selection  of 
food,  in  the  choice  of  a  flower  or  object  of  one  color  in 
preference  to  another,  in  perceiving  likeness  or  unlikeness  in 
two  objects,  indicates  that  they  can  exercise  the  power  of 
intelligent  discrimination,  as  has  been  said  by  Mr.  G.  H. 
Lewes  :*  "  When  there  is  no  alternative  open  to  an  action 
it  is  impulsive  ;  when  there  is,  or  originally  was,  an  alter- 
native, the  action  is  instinctive  ;  where  there  are  alterna- 
tives which  may  still  determine  the  action,  and  the  choice 
is  free,  we  call  the  action  intelligent." 

Indeed,  animals  have  the  principle  of  similarity  strongly 
developed.  It  is  the  bond  that  holds  together  the  social  or- 
ganizations of  such  insects  as  live  in  colonies,  and  such  fish, 
birds,  or  mammals  as  go  in  schools,  flocks,  or  herds.  Were 
it  not  for  this  mental  quality  some  species  would  tend  to 
die  out. 

Animals  possess  memory,  which  consists  in  storing  up  in 
the  mind  the  results  of  external  impressions,  so  that  they 
are  enabled  to  perceive  the  points  of  resemblance  or  differ- 
ence between  two  objects,  after  having  been  out  of  sight  of 
them  for  a  greater  or  less  length  of  time.  Bain  defines 
memory,  acquisition  or  retention,  as  "  being  the  power  of 
continuing  in  the  mind  impressions  that  are  no  longer  stim- 
ulated by  the  same  agent,  and  of  recalling  them  afterward 
by  purely  mental  forces. " 

With  the  aid  of  memory,  birds  make  their  migrations, 
bees  and  ants  find  their  way  back  to  their  nests.  As  wo 
have  elsewhere  said,  "  No  automaton  could  find  its  way 
back  to  a  point  from  which  it  had  once  started,  however 
well  the  machine  had  been  originally  wound  up.  Nor  does 
the  common  notion  of  an  inflexible  instinct  meet  the  case. 
Memory  is  often  due  to  a  repetition  of  certain  experiences, 
and  experiences  lay  the  foundation  for  instinctive  acts  ;  it 
is  the  sum  of  these  inherited  experiences  which  make  up 
the  total  which  passes  under  the  name  of  instinct,  "f 

*  Article  on  Instinct  in  Nature,  April  10th,  1873. 
f  Half  Hours  with  Insects,  p.  374. 


682  ZOOLOGY. 

It  would  appear,  then,  that  animals  have  in  some  slight 
degree  what  we  call  mind,  with  its  threefold  divisions  of  the 
sensibilities,  intellect,  and  will.  When  we  study  animals  in 
a  state  of  domestication,  especially  the  dog  or  horse,  we 
know  that  they  are  capable  of  some  degree  of  education, 
and  that  they  transmit  the  new  traits  or  habits  which  they 
have  been  taught  to  their  offspring  ;  so  that  what  in  the 
parents  were  newly  acquired  habits  become  in  the  descend- 
ants instinctive  acts.  We  are  thus  led  to  suppose  that  the 
terse  definition  of  instinct  by  Murphy,  that  it  is  "  the  sum 
of  inherited  habits,"  is  in  accordance  with  observed  facts. 
Indeed,  if  animals  have  sufficient  intelligence  to  meet  the 
extraordinary  emergencies  of  their  lives,  their  daily,  so- 
called  instinctive  acts,  requiring  a  minimum  expenditure  of 
mental  energy,  may  have  originated  in  previous  genera- 
tions, and  this  suggests  that  the  instincts  of  the  present 
generation  may  be  the  sum  total  of  the  inherited  mental  ex- 
periences of  former  generations. 

Descartes  believed  that  animals  are  automata.  Lamarck 
expressed  the  opinion  that  instincts  were  due  to  certain  in- 
herent inclinations  arising  from  habits  impressed  upon  the 
organs  of  the  animals  concerned  in  producing  them. 

Darwin  does  not  attempt  any  definition  of  instinct ;  but 
he  suggests  that  "  several  distinct  mental  actions  are  com- 
monly embraced  by  this  term,"  and  adds  that  "  a  little 
dose,  as  Pierre  Huber  expresses  it,  of  judgment  or  reason 
often  comes  into  play,  even  in  animals  low  in  the  scale  of 
nature."  He  indicates  the  points  of  resemblance  between 
instincts  and  habits,  shows  that  habitual  action  may  become 
inherited,  especially  in  animals  under  domestication  ;  and 
since  habitual  action  does  sometimes  become  inherited,  he 
thinks  it  follows  that  ' '  the  resemblance  between  what  origi- 
nally was  a  habit  and  an  instinct  becomes  so  close  as  not  to 
be  distinguished. "  He  concludes  that,  by  natural  selection, 
slight  modifications  of  instinct  which  are  in  any  way  useful 
accumulate,  and  thus  animals  have  slowly  and  gradu- 
ally, "  as  small  consequences  of  one  general  law,"  acquired, 
through  successive  generations,  their  power  of  acting  in- 


INSTINCT  AND  REASON.  683 

stinctively,  and  that  they  were  not  suddenly  or  specially 
endowed  with  instincts. 

Rev.  J.  J.  Murphy,  in  his  work  entitled  "  Habit  and  In- 
telligence," seems  to  regard  instinct  as  the  sum  of  inherited 
habits,  remarking  that  "  reason  differs  from  instinct  only 
in  being  conscious.  Instinct  is  unconscious  reason,  and 
reason  is  conscious  instinct."  This  seems  equivalent  to 
saying  that  most  of  the  instincts  of  the  present  generation 
of  animals  is  unconscious  automatism,  but  that  in  the  begin- 
ning, in  the  ancestors  of  the  present  races,  instincts  were 
more  plastic  than  now,  such  traits  as  were  useful  to  the  or- 
ganism being  preserved  and  crystallized,  as  it  were,  into  the 
instinctive  acts  of  their  lives.  This  does  not  exclude  the 
idea  that  animals,  while  in  most  respects  automata,  occa- 
sionally perform  acts  which  transcend  instinct ;  that  they 
are  still  modified  by  circumstances,  especially  those  species 
which  in  any  way  come  in  contact  with  man  ;  are  still  in  a  de- 
gree free  agents,  and  have  unconsciously  learned,  by  success 
or  failure,  to  adapt  themselves  to  new  surroundings.  This 
view  is  strengthened  by  the  fact  that  there  is  a  marked  de- 
gree of  individuality  among  animals.  Some  individuals  o^ 
the  same  species  are  much  more  intelligent  than  others, 
they  act  as  leaders  in  different  operations.  Among  dogs, 
horses,  and  other  domestic  animals,  those  of  dull  intellect 
are  led  or  excelled  by  those  of  greater  intelligence,  and  this 
indicates  that  they  are  not  simply  automata,  but  are  also  in 
a  degree,  or  within  their  own  sphere,  free  agents. 


BIBLIOGEAPHY.* 


GENERAL   ZOOLOGY. 

Elements  of  Comparative  Anatomy.  By  Carl  Gegenbaur.  London, 
1878. 

A  Manual  of  the  Anatomy  of  Vertebrated  Animals.  By  T.  H.  Hux- 
ley. London,  1871. 

A  Manual  of  the  Anatomy  of  Invertebrated  Animals.  By  T.  H. 
Huxley.  New  York,  1878. 

Forms  of  Antmai  Life.     By  George  Rolleston.     Oxford,  1870. 

Grundziige  der  Zoologie.  Von  C.  Glaus.  Leipzig,  1876.  Fourth 
edition,  1879. 

Handbuch  der  Zoologie.  Band  1,  Wirbelthiere,  Mollusken  und  Mol- 
luscoiden,  von  J.  Victor  Cams,  Leipzig,  1868-1875  ;  Band  2,  Arthropo- 
den,  von  A.  Gerstaecker  ;  Raderthiere,  Wiirmer,  Echinodermen,  Ccelen- 
teraten  und  Protozoen,  von  J.  Victor  Carus,  Leipzig,  1863. 

Bronn's  Classen  und  Ordnungen  der  Thierreichs.  Protozoa,  Radiata, 
Crustacea,  Amphibia.  (Other  parts  incomplete.)  Leipzig  und  Heidel- 
berg. 

Zoologie.  Von  L.  K.  Schmarda.  2te.  Auflage.  Band  1,  2.  Wien, 
1877-78. 

The  Anatomy  of  Vertebrates.     By  R.Owen.     3vols.     London,  1868. 

A  Key  to  the  Birds  of  North  America.  By  Elliott  Coues.  Boston, 
1872. 

The  Birds  of  North  America.  3  vols.  By  S.  F.  Baird,  T.  M. 
Brewer,  and  R.  Ridgway.  Land  Birds.  Boston,  1874. 

Contributions  to  the  Natural  History  of  the  United  States.  By  L. 
Agassiz.  4  vols.  Boston,  1857-1862. 

Mind  in  Nature.     By  H.  J.  Clark.     New  York,  1865. 

Manual  of  the  Vertebrates  of  the  Northern  United  States.  By  D.  S. 
Jordan.  Second  edition.  Chicago,  1878. 

Seaside  Studies  in  Natural  History.  By  E.  C.  Agassiz  and  Alexander 
Agassiz.  Radiata.  Boston,  second  edition,  1871. 

Introduction  to  Entomology.  By  W.  Kirby  and  W.  Spence.  4  vols. 
London,  1828. 

*  Works  used  in  the  preparation  of  this  volume,  with  the  titles  of  others  indispen- 
sable to  the  student. 


686  ZOOLOGY. 

Manual  of  Entomology.     By  H.  Burmeister.     London,  1836. 

Guide  to  the  Study  of  Insects.  By  A.  8.  Packard,  Jr.  Seventh 
edition.  New  York,  1880. 

Invertebrate  Animals  of  Vineyard  Sound.  By  A.  E.  Verrill.  (Re- 
port U.  S.  Commissioner  of  Fish  and  Fisheries.)  Washington,  1873. 

Inver'tebrata  of  Massachusetts.  By  A.  A.  Gould.  Edited  by  W.  G. 
Binney.  Boston,  1870. 

First  Book  of  Zoology.  By  E.  S.  Morse.  Second  edition.  New 
York,  1875. 

Manual  of  the  Mollusca.  By  S.  P.  Woodward.  Second  edition. 
London,  1868. 

Corals  and  Coral  Islands.     By  J.  D.  Dana.     New  York,  1872. 

Introduction  to  the  Osteology  of  Mammalia.  By  W.  H.  Flower. 
London,  1870. 

Advanced  Text-Book  of  Zoology.  By  H.  A.  Nicholson.  New 
York,  1873. 

Elementary  Biology.  By  T.  II.  Huxley  and  H.  N.  Martin.  New 
York,  1876. 

With  the  works  and  monographs  of  Dana,  Wymaii,  Leidy,  L.  and  A. 
Agassiz,  H.  J.  Clark,  Cope,  Gill,  Hyatt,  Verrill,  Scudder,  Binney, 
Allen,  Coues,  Smith,  Baird,  Ridgway,  Brewer,  Dall,  Cooper,  Wilder, 
Riley,  Uhler,  Edwards,  Grote,  Le  Conte,  Hagen,  Scammon,  Stimpson, 
Jordan,  Morse,  Thomas,  Gould,  Bland,  Prime,  Tryon,  Gabb,  Packard, 
and  others,  and  the  standard  works  of  Linnaeus,  Cuvier,  Von  Baer, 
Leuckart,  Gegenbaur,  Haeckel,  St.  Hilaire,  Huxley,  Mivart,  Allman, 
Hincks,  Shuckard,  Westwood,  P.  J.  and  E.  Van  Beneden,  Brandt, 
Ratzburg,  Burmeister,  Oscar  Schmidt,  Metschnikoff,  Kowalevsky, 
Kupffer,  and  many  others. 

The  student  should  also  consult  the  following  serials  :  American  Jour- 
nal of  Science  and  Arts,  New  Haven,  Conn.  ;  The  American  Naturalist, 
Philadelphia  ;  Nature,  London  ;  Quarterly  Journal  of  Microscopical 
Science,  London  ;  Archiv  fur  Naturgeschichte,  Berlin  ;  Annals  and 
Magazine  of  Natural  History,  London  ;  Annales  des  Sciences  Naturelles, 
Zoologie,  Paris  ;  Siebold  und  Kolliker's  Zeitschrift,  Canadian  Ento- 
mologist, London,  Canada  ;  Psyche,  Cambridge. 

Descriptions  of  North  American  animals  and  essays  on  their  anatomy, 
physiology,  and  development  are  to  be  found  in  the  Transactions  and 
Proceedings  of  the  following  scientific  societies  :  American  Academy 
of  Arts  and  Sciences,  Boston  ;  American  Philosophical  Society,  Phila- 
delphia ;  Academy  of  Natural  Sciences,  Philadelphia  ;  Boston  Society 
of  Natural  History  ;  Smithsonian  Institution  ;  American  Entomologi- 
cal Society,  Philadelphia  ;  Museum  of  Comparative  Zoology,  Cam- 
bridge, Mass.  ;  Essex  Institute  ;  Peabody  Academy  of  Science,  Salem; 
Academy  of  Sciences,  San  Francisco,  Cal.  ;  and  other  societies  in  Port- 
land, Me.  ;  Buffalo,  N.  Y.  ;  Davenport,  Iowa  ;  St.  Louis,  Mo. ,  and 
Charleston,  S.  C.  ;  New  York  and  New  Haven. 


BIBLIOGRAPHY.  687 

HISTOLOGY. 

Handbook  of  Human  and  Comparative  Histology.  By  S.  Strieker. 
New  York,  1872. 

And  the  monographs  or  essays  of  Leidy,  Clark,  and  C.  S.  Minot. 

PHYSIOLOGY. 

Treatise  on  Human  Physiology.  By  J.  C.  Dalton.  Philadelphia, 
1361. 

Elementary  Lessons  in  Physiology.  By  T.  H.  Huxley.  Fourth 
edition.  London,  1870. 

Text-Book  of  Physiology.     By  M.  Foster.     London,  1877. 

EMBRYOLOGY. 

Entwicklungsgeschichte  der  Thiere.  Von  Baer.  Konigsberg, 
1828. 

Entwicklungsgeschichte  des  Menschen.  Von  A.  Kolliker.  Leip- 
zig, 1861. 

Elements  of  Embryology.  By  M.  Foster  and  F.  M.  Balfour,  Lon- 
don, 1874. 

With  the  monographs  of  Wolff,  Harvey,  Barry,  Coste,  Pouchet, 
Von  Baer,  Remak,  Bischoff,  L.  and  A.  Agassiz,  Weismann,  Metsch- 
nikoff,  Huxley,  Balfour,  Parker,  and  others. 

ZOOGEOGRAPHY. 

The  Geographical  Distribution  of  Animals.  By  A.  R.  Wallace. 
2  vols.  New  York,  1876. 

With  the  essays  of  Agassiz,  Baird,  Allen,  Verrill,  Ridgway,  Gill, 
Packard,  and  others. 

EVOLUTION  AND  RELATION   OF  ANIMALS   TO  THEIR  ENVIRONMENT. 

Philosophic  Zoologique.     a  J.  B.  de  Lamarck.     8vo,  2  vols.     1809. 

On  the  Origin  of  Species.     By  Charles  Darwin.     New  York,  1871. 

The  Origin  of  Genera.     By  E.  D.  Cope.     Philadelphia,  1861. 

Contributions  to  the  Theory  of  Natural  Selection.  By  A.  R.  Wal- 
lace. New  York,  1&70. 

On  the  Origin  of  Species.     By  T.  H.  Huxley.     New  York,  1863. 

With  the  essays  of  Cope,  Hyatt,  Wagner,  Weismann,  Haeckel, 
Kupffer,  Palmen,  Lubbock,  and  others. 

NATURAL  HISTORY  OF  MAN. 

Do  Generis  Humani  Varietate  Nativa.  Von  J.  F.  Blumenbach. 
Editio  3.  Gottingen,  1795. 


688  ZOOLOGY. 

Researches  into  the  Physical  History  of  Mankind.     By  J.  C.  Prich- 
ard.    London,  1851. 

Types  of  Mankind.  By  J.  C.  Nott  and  G.  R.  Gliddon.  Philadel- 
phia, 1854. 

Natural  History  of  the  Varieties  of  Man.  By  R.  G.  Latham.  Lon- 
don, 1850. 

Races  of  Man.     By  Charles  Pickering.     London,  1863. 

Evidence  as  to  Man's  Place  in  Nature.  By  T.  H.  Huxley.  New 
York,  1863. 

Prehistoric  Times.     By  Sir  John  Lubbock.     London,  1872. 

Natural  History  of  the  Human  Species.  By  H.  Smith.  Edinburgh, 
1852. 

With  the  works  and  essays  of  Retzius,  Wilson,  Mortillet,  Broca, 
Lartet,  Von  Baer,  St.  Hilaire,  8.  Van  der  Kolk,  Vrolik,  Schaaffhausen, 
Riitimeyer,  Busk,  Morgan,  Wyman,  Squire,  Davis,  Schmerling,  Wag 
ner,  Vogt,  Rolle,  and  others. 


GLOSS  AEY. 


ABDOMEN.  In  mammals  the  part 
of  the  trunk  below  or  behind  the 
thorax  ;  in  insects  the  third  re- 
gion of  the  body,  or  hind  body. 

ABERRANT.  Departing  from  the 
regular  or  normal  type. 

ABORAL.  Opposite  the  oral  or 
mouth-region. 

ACUMINATE.  Ending  in  a  pro- 
longed point. 

ALVEOLUS.  A  hollow  cavity 
forming  the  socket  in  the  jaw 
of  vertebrates  for  the  teeth. 

AMBULACRUM  (Lat.  from  ambu- 
lare,  to  walk,  a  garden-walk). 
The  perforated  space  or  area  in 
the  shell  of  the  sea-urchin  or  the 
arm  of  a  star-fish,  through  which 
the  foot-tubes  or  ambulacral 
feet  are  protruded. 

AMETABOLIC  (Gr.  a,  without ; 
metabole,  change).  Referring  to 
insects  and  other  animals  which 
do  not  undergo  a  metamorpho- 
sis. 

AMORPHOUS  (Gr.  a,  privitive  ; 
morphe,  form).  Without  a  defi- 
nite figure  ;  shapeless  ;  especially 
applicable  to  sponges. 

AMPHICCELOUS  (Gr.  amphi ;  koilos, 
hollow).  Applied  to  vertebrae 
which  are  doubly  concave,  or 
hollow  at  both  ends. 

ANASTOMOSING.     Inosculating  or 


running  into  each  other  like 
veins. 

ANCHYLOSIS.  The  growing  to- 
gether of  two  bones  so  as  to  pre- 
vent motion  between  them. 

ANNULATE.  When  a  leg  or  antenna 
is  surrounded  by  narrow  rings 
of  a  different  color. 

APLACENTAL.  Referring  to  those 
mammals  in  which  the  embryos 
are  destitute  of  a  placenta. 

APODOUS.     Footless. 

APTEROUS  (Gr.  a,  without ;  pteron, 
wing).  Destitute  of  wings. 

AQUIFEROUS  (Lat.  aqua,  water ; 
few,  I  carry).  Applied  to  the 
water-carrying  or  water- vascular 
system  of  the  sponges,  etc. 

AREOLATE.  Furnished  with  small 
areas  ;  like  a  net-work. 

ARISTATE.    Furnished  with  a  hair. 

ARTHROPODA  (Gr.  a,  without ; 
arthros,  a  -joint ;  pous,  podos, 
foot).  Those  Articulata  with 
jointed  feet. 

ARTICULATA  (Lat.  articulw,  di- 
minutive of  artus,  a  joint). 
Cuvier's  subkingdom  of  worms, 
Crustacea  and  insects. 

ARTIODACTYLA  (Gr.  artios,  even  ; 
daktulos,  finger  or  toe).  Those 
Ungulates  with  an  even  number 
of  toes,  as  the  ox. 

ASEXUAL.     Applied   to    animals, 


690 


ZOOLOGY. 


especially  insects,  in  which  the 
ovaries  or  reproductive  organs 
are  imperfectly  developed  ;  and 
which  produce  eggs  or  young  by 
budding. 

AURELIA.  Old  term  for  the  pupa 
of  an  insect. 

AURICLE  (Lat.  auricula,  a  little 
ear).  One  of  the  cavities  of  the 
heart  of  mollusks  and  verte- 
brates. 

AZYGOS  (a,  without ;  zugon,  a 
yoke,  a  pair).  An  organ,  such  as 
a  nerve  or  artery,  situated  in  the 
middle  line  of  a  bilaterally  sym- 
metrical animal,  which  has 
therefore  no  fellow. 

BLASTODERM  (blastos,  a  bud  or 
sprout ;  derma,  skin).  The  outer 
layer  of  the  germ -cells  of  the 
embryo. 

BIFID.  Divided  into  two  parts  ; 
forked. 

BRANCHIA.  A  gill  or  respiratory 
organ  of  aquatic  animals. 

BUCCAL.  Relating  to  the  mouth 
or  cheeks. 

BULLATE.    Blistered. 

CADUCIBRANCHIATE  (Lat.  caducus, 
falling  off  ;  Gr.  bragchia,  gills). 
Applied  to  those  Batrachia  in 
which  the  gills  become  absorbed 
before  adult  life. 

CALCARATED.     Armed  with  spurs. 

CALYX.  A  little  cup  ;  often  ap- 
plied to  the  body  of  a  Crinoid. 

CAPITATE.  Ending  in  a  head  or 
knob. 

CHELA.  The  terminal  portion  of 
a  limb  with  a  movable  lateral 
part,  like  the  claw  of  a  crab  ;  as 
in  the  chelate  maxilla  of  the 
scorpion. 

CHI  ASM  A  (Gr.  chiasma,  a  crossing.) 


The  commissure  of  the  optic 
nerves  in  most  vertebrates. 

CHITIN  (Gr.  chiton,  a  tunic).  The 
horny  covering  of  insects,  etc. 

CHYLE  (Gr.  chulos,  juice).  The 
milky  fluid  resulting  from  the 
action  of  the  digestive  fluids  on 
the  food  or  chyme. 

CHYME  (Gr.  chumos,  juice).  The 
acid,  partly  fluid  or  partly  di- 
gested food,  produced  by  the  ac- 
tion of  the  gastric  juice  on  the 
food. 

CTLIUM  (pi.  cilia).  Microscopic 
filaments  attached  to  cells,  usu- 
ally within  the  body,  and  mov- 
ing usually  rhythmically, 

CCECAL.  Ending  blindly  or  in  a 
cul-de-sac. 

CCECUM.  A  blind  sac;  usually  ap- 
plied to  one  or  more  append- 
ages of  the  digestive  canal. 

CGENENCHYMA  (Gr.  koinos,  com- 
mon ;  chumos,  chyme  or  juice). 
Applied  in  polyps  to  the  coral 
mass  containing  the  chymiferous 
or  nutritive  canals  connecting  the 
different  polyps. 

COMMISSURE.  The  nerves  con- 
necting two  ganglia. 

CONCOLOROUS.  Of  the  same  color 
as  another  part. 

CONDYLE  (Gr.  kondulos,  a 
knuckle).  The  articular  sur- 
face of  a  bone,  especially  of  the 
occiput. 

CORTICAL.  Relating  to  the  cortex 
or  inner  skin  ;  external  as  op- 
posed to  medullary. 

COSTAL  (Lat.  costa,  a  rib).  Relat- 
ing to  the  ribs. 

CRIBRIFORM  (Lat.cn&rwm,  a  sieve  ; 
forma,  form).  With  perfora- 
tions like  those  of  a  sieve. 

CROP.  A  partial  dilatation  of  the 
gullet  or  oesophagus,  the  inglu- 


GLOSSARY. 


691 


vies  ;  in  many  insects  the  fore 
stomach  or  proventriculus. 
CUTICLE.     The  outermost  layer  of 
the  integument. 

DENTATE.    Furnished  with  teeth. 

DIDELPHIA  (Gr.  dis,  two,  or  dou- 
ble.; delphus,  womb).  The  sub- 
class of  Marsupials. 

DIFFERENTIATION.  The  special- 
ization or  setting  apart  of  special 
organs  for  special  work,  as  the 
specialization  of  the  hand  of  man 
from  the  fore-foot  of  other  mam- 
mals ;  also  applied  to  the  special 
development  during  embryonic 
life  of  parts  adapted  for  peculiar 
or  special  functions. 

DIMIDIATE.     Half  round. 

DIOECIOUS  (Gr.  dis,  two  ;  oikos, 
house).  With  distinct  sexes. 

DIPTERA  (Gr.  dis,  two  ;  pteron, 
wing).  Two-winged  flies ;  tin 
order  of  insects. 

DIVERTICULUM.  An  offshoot 
from  a  vessel  or  from  the 
alimentary  canal. 

ECDYSIS  (Gr.  ekdusis,  casting  off). 
The  process  of  casting  the  skin  ; 
moulting. 

ECHINODERMATA  (Gr.  echinos,  a 
hedgehog  or  urchin  ;  hence  ap- 
plied to  the  sea-urchin ;  and 
derma,  skin).  The  fourth  sub- 
kingdom  of  animals. 

ELASMOBRANCHII  (Gr.  elasma,  a 
strap ;  bragchia,  gill).  The 
sharks  and  rays. 

ELYTRA  (Gr.  elutron,  a  sheath). 
The  fore-wings  of  beetles,  serv- 
ing to  cover  or  sheathe  the  hind 
wings. 

EPISTOMA.  That  part  of  the  face 
of  flies  situated  between  the 
front  and  the  labrum. 


EQUILATERAL.  Having  the  sides 
equal,  as  in  Brachiopod  shells. 

EQUIVALVE.  Applied  to  shells  like 
the  clams  and  most  Lamelli- 
branchs,  which  are  composed 
of  two  equal  pieces  or  valves. 

EXSERTED.  Protruded  ,  opposed 
to  enclosed. 

EXUVIUM.     Cast-off  skin. 

FISSIPAROUS  (Lat.  fissus,  cleft  •, 
pario,  to  bring  forth).  Applied 
to  a,  form  of  asexual  generation 
where  the  parent  splits  into  two 
parts,  each  part  becoming  a  new 
individual. 

GEMMIPAROUS  (gemma,  bud ; 
pario,  to  bring  forth).  Applied 
to  a  form  of  asexual  generation 
where  new  individuals  arise  as 
buds  from  the  body  of  the 
parent. 

GLABROUS.  Smooth  ;  opposed  to 
hairy  ;  downy,  villous. 

GLAUCOUS.     Bluish  green  or  gray. 

HAEMAL  (Gr.  Jiaima,  blood). 
Connected  with  the  blood-ves- 
sels or  heart. 

HALTERES  (Gr.  Jialteres,  poisers). 
Balancers ;  the  rudimentary 
hind  wings  of  Diptera. 

HAUSTELLATE.  Furnished  with  a 
proboscis  so  as  to  take  food  by 
suction. 

HEMIPTERA  (Gr.  hemi,  half;  pteron, 
wing).  An  order  of  insects  with 
the  fore-wings  partly  opaque, 
hence  called  hemelytra. 

HERMAPHRODITE  (Gr.  Hermes, 
Mercury ;  Aphrodite,  Venus). 
Any  animal  having  the  organs  of 
both  sexes,  usually  the  ovary 
and  testes,  combined  in  the  same 
individual. 


692 


ZOOLOGY. 


HEXAPODOUS.  Provided  with  six 
feet. 

HYMENOPTERA  (Gr.  humen,  hy- 
men, or  membrane ;  pteron, 
wing).  An  order  of  insects  with 
two  pairs  of  membranous  wings. 

HYOID  (Gr.  T,  eidos,  resemblance). 
A  bone  in  man  named  from  re- 
sembling ihe  letter  U  ;  its  form 
being  different  in  other  verte- 
brates :  also  called  os  linguce, 
from  its  supporting  the  tongue. 

IMAGO.  The  final  or  fourth, 
winged  and  adult  state  of  insects. 

INEQUILATERAL  Having  the  two 
ends  unequal,  as  in  the  clam, 
quohog,  and  most  Lamelli- 
branch  shells. 

INEQUIVALVE.  With  one  valve 
differing  in  size  or  shape  from 
the  other,  as  in  the  oyster  or 
Brachiopod  shells. 

IRRORATED.  Freckled ;  sprinkled 
with  atoms. 

LAMELLIBRANCHIATA  (Lat.  la- 
mella, a  leaf  or  sheet ;  branckia, 
gill).  A  class  of  mollusks  with 
large  leaf -like  gills. 

LARVA  (Lat.  larva,  a  mask). 
The  second  stage  of  the  insect,  a 
caterpillar,  grub,  or  maggot. 

LUMBAR  (Lat.  lumbus,  a  loin). 
Connected  with  the  loins. 

MONCECIOUS  (Gr.  monos,  single ; 
oikos,  house).  With  the  sexual 
glands,  etc.,  united  in  the  same 
individual. 

NEMATOCYST  (Gr.  nema,  a  thread  ; 
kustis,  a  bladder).  The  nettling, 
stinging  organs  or  thread-cells 
or  lasso-cells  of  the  jelly-fishes 
and  polyps,  etc. 


NEUROPTERA  (Gr.  neuron,  a  cord  ; 
pteron,  wing).  The  order  of 
net-veined  insects. 

NIDAMENTAL.  Referring  to  a 
nest,  or  egg-sac. 

NOTOCHORD  (Gr.  noton,  back ; 
chorde,  a  string),  or  chorda 
dorsalis.  The  primitive  support 
of  the  body  of  vertebrate  embry- 
os, larval  ascidians,  and  the  back- 
bone of  the  lancelet  and  lam- 
preys. 

DETECTED.     Covered  ;  concealed. 

ODONTOPHORE  (Gr.  odous,  a  tooth  ; 
phero,  I  carry).  The  so-called 
tongue  or  lingual  ribbon  of  the 
higher  mollusks. 

(ESOPHAGUS  (Gr.  oisos,  a  reed ; 
phagein,  to  eat).  The  gullet. 

OPERCULUM  (Lat.  operio,  to  cover). 
In  fishes  one  or  more  bones 
covering  the  gills  ;  in  Gastropod 
Mollusks  a  horny  plate  or  solid 
limestone  mass  closing  the  orifice 
of  shells. 

OPISTHOCCELOUS  (Gr.  opisthen,  be- 
hind ;  koilos,  hollow).  Those 
vertebrates  with  bodies  hollow 
behind  and  convex  in  front. 

ORAL.     Related  to  the  mouth. 

ORNITHODELPHIA  (Gr.  ornis,  bird  ; 
delphus,  womb).  The  sub -class 
of  mammals  and  order  Monotre- 
mala. 

ORTHOPTERA  (Gr.  orthos,  straight ; 
pteron,  wing).  The  order  of 
insects  with  straight  narrow  fore- 
wings,  as  the  grasshoppers. 

OSTRACODA  (Gr.  osiracodes.  shelled). 
A  group  of  shelled  Crustacea. 

OTOLITHS  (Gr.  ous,  ear ;  lithos, 
stone).  Small  bones  suspended 
in  the  internal  ear  of  fishes,  or 
concretions  in  the  auditory  sacs 
of  invertebrates. 


GLOSSARY. 


693 


OVIPAKOUS  (Lat.  ovum,   an  egg 
pario,   I  bring  forth).      Appliec 
to  animals  bringing  forth  eggs 
instead  of  living,  active  young. 

OVIPOSITOR  (Lat.  ovum,  an  egg 
pono,  I  place).     An  organ  in  in- 
sects homologous  with  the  sting, 
by  which  eggs  are  deposited  in 
solid  substances. 

O  vis  AC.  A  sac  or  bag-like  mem- 
brane attached  to  the  parent, 
and  containing  eggs. 

OVO-VIVIPAROUS  (Lat.  ovum,  an 
egg  ;  vivus,  alive  ;  pario,  I  bring 
forth).  Applied  to  such  animals 
as  retain  their  eggs  in  the'  body 
until  they  are  hatched. 


PALLIUM  (Lat.  a  cloak).  The  man- 
tle or  body-wall  of  mollusks, 
which  secretes  the  shell ;  adj. 
pallial. 

PARENCHYMA  (Gr.  paregchuma, 
from  para,  en,  chuo,  something 
poured  in  besides).  Applied  to 
the  proper  substance  of  viscera, 
excluding  connective  tissue, 
blood-vessels,  and  other  accesso- 
ry parts. 

PELAGIC.  Living  on  the  high 
seas,  away  from  the  coast ;  in 
mid-ocean. 

PERISOME  (Gr.  peri,  around  ;  soma, 
body).  In  Crinoids  the  oral  re- 
gion of  the  cup  or  body. 

PERRENNIBRANCHIATA  (Lat.  per- 
ennis,  perennial  ;  branchia,  gill). 
Those  Batrachia  which  retain 
their  gills  throughout  life. 

PERISSODACTYLA  (Gr.  penssos,  un- 
even ;  daktulos,  finger).  Those 
Ungulates  with  an  uneven  num- 
ber of  toes,  as  the  horse. 

PERITONEUM  (Gr.  peri,  around ; 
teino,  I  stretch).  The  membrane 


lining  the  abdominal  walls  and 
covering  the  enclosed  viscera. 
PERIVISCERAL  (Gr.  peri,  around  ; 
Lat.  viscera,  the  internal  organs, 
especially  of  the  abdominal  cav- 
ity).    The  body-cavity  contain- 
ing the  alimentary  canal  with 
its  outgrowths. 
PICEOUS.      Pitchy  ;  the  color  of 

pitch  ;  shining  reddish  black. 
PILOSE.     Clothed    with   pile,   or 

dense  short  down. 
PLEXUS  (Lat.    a  knot).      Applied 
to  a  knot-like  mass    of  nerves 
or  blood-vessels. 

POLYPIDE  or  POLYPITE.  The 
separate  animals  of  a  Hydro- 
zoon. 

PREORAL.    In  front  of  the  mouth. 
PROCESS.      A    projection ;     used 

chiefly  in  osteology. 
PROCOELOUS  (Gr.  pro,  front ;  koilos, 
hollow).      Those  vertebrae  con- 
cave or  hollow  in  front. 
PROTOPLASM    (Gr.    protos,    first ; 
plasma,  from  plasso,   I  mould). 
The     albuminous,     elementary 
matter  forming    cells  and  the 
body-substance  of  frotozoa. 
PROXIMAL  (Lat.  praximus,  next). 
The  fixed  end  of  a  limb,  bone  or 
appendage ;     that    nearest    the 
body  ;    opposed  to    distal,    the 
farther  end. 
PSEUDOPODIA  (Gr.  pseudes,  false  ; 
podes,  feet).    The  temporary  pro- 
cesses sent  out  from  the  bodies 
of  Protozoa. 

PTEROPODA  (Gr.  pteron,  wing ; 
podes,  feet).  A  class  of  pelagic 
mollusks. 

.PUBESCENT.  Coated  with  very 
fine  hairs. 

UNCTURED.     Marked   with    nu- 
merous small  impressed  dots. 
PUPA  (Lat.  a  doll).     The  third  or 


694 


ZOOLOG  T. 


usually      quiescent,      chrysalis 
stage  of  insects. 

RATIT.E  (Lat.  ratis,  a  raft).  A 
division  of  birds  with  a  keelless, 
raft  or  punt-like  sternum. 

KHIZOPODA  (Gr.  riza,  root ;  pous, 
podos,  foot).  The  root-footed 
Protozoa. 

ROTIFERA  (Lat.  rota,  a  wheel ; 
fero,  I  bear).  An  order  of  cms- 
tacea  with  a  pair  of  ciliated  vela 
in  motion,  resembling  wheels. 

SARCODE  (Gr.  sarx,  flesh ;  odos, 
way).  Equivalent  and  earlier 
term  for  protoplasm. 

SCABROUS.  Rough  like  a  file , 
with  small  raised  dots. 

SETACEOUS  (Lat,  seta,  a  bristle). 
Bristle-like. 

SPIRACLE  (Lat.  spiro,  to  breathe). 
The  lateral  breathing  pores  of 
insects. 

STIGMATA  (Gr.  stigma,  a  mark).  A 
synonym  of  spiracle. 

STOLON  (Lat.  stolo,  a  shoot  spring- 
ing from  the  root  of  a  plant). 
Applied  to  the  root-like  creeping 
growths  of  polyps  and  other  Cce- 
lenterates. 

STREPSIPTERA  (GT.strephis,Si  twist; 
pteron,v?ing).  A  group  of  beetles, 
whose  minute  front  wings  appear 
as  if  twisted. 

STROBILA  (Gr.  stroMos,  a  fir  cone). 
The  chain  of  zooids  of  a  larval 
medusa  ;  the  chain  of  proglot- 
tides  of  a  tape-worm. 

SUTURE.  A  seam  or  impressed 
line  between  the  bones  of  the 
skull  or  parts  of  the  crust  of  an 
Arthropod. 

SYMPHYSIS  (Gr.  sumphusis,  a  grow- 
ing together).  The  union  of 
two  bones. 


TELSON  (Gr.  telson,  from  telos.  end). 
The  rudimentary  terminal  seg- 
ment of  the  abdomen  of  Arthro- 
pods. 

TENERAL.  A  state  of  the  Neurop- 
terous  imago  after  exclusion 
from  the  pupa,  in  which  it  has 
not  fully  completed  its  coloring, 
clothing,  etc. 

TENTACULUM  (Lat.  tento,  I  touch). 
A  feeler  or  tentacle. 

TERGUM  (Lat.  back).  The  dorsal 
region  of  Arthropods. 

TEST  (Lat.  testa,  n  shell).  The 
thickened  integument  of  Tuni- 
cata. 

TESTACEOUS.  Dull  red ;  brick 
color. 

THORAX  (Gr.  thorax,  a  breast- 
plate). The  chest  in  verte- 
brates ;  the  middle  body  in  in- 
sects and  some  Crustacea. 

THYSANURA  (Gr.  thusanoi,  fringes  ; 
oura,  tail).  The  lowest  order  of 
insects. 

TOMENTOSE.  Covered  with  fine 
matted  hairs. 

TRABECUL^  (cranii),  dim.  of 
trabs,  a  beam.  Applied  to  the 
longitudinal  cartilaginous  bars  of 
the  fore-part  of  the  head  of  ver- 
tebrate embryos. 

TRACHEA  (Gr.  trachda,  the  rough 
windpipe).  The  respiratory 
tube  in  vertebrates ;  the  air- 
tube  of  Tracheate  insects. 

TREMATODA  (Gr.  trema,  a  pore 
or  hole).  An  order  of 
worms. 

TRUNCATED.  Cut  squarely  off  ; 
docked. 

TUBERCULOSE.  Covered  with  tu- 
bercles. 

TUNICATA  (Lat.  tunica,  a  cloak). 
The  class  of  worms  called  As- 
cidians. 


GLOSSARY. 


695 


UMBO  (Lat.  the  boss  of  a  shield). 
The  beak  of  a  Lamellibranchiate 
shell. 

UNGULATA  (Lat.  ungula,  a  hoof). 
The  order  of  hoofed  mammals. 

UnoDELA(Gr.0wra,  tail ;  delos, visi- 
ble). The  tailed  Batrachians. 


VACUOLE  (Lat.  vacuus,  empty). 
The  little  cavities  in  the  bodies 
of  Protozoa. 

VENTRAL.  Applied  to  the  under 
side  of  the  abdomen,  or  of  the 
body  of  invertebrates. 

VENTRICLE  (Lat.  ventriculus, 
diminutive  of  venter,  belly).  One 
of  the  cavities  of  the  heart. 

VERRICULATE.  With  thick  -  set 
tufts  of  parallel  hairs. 

VERRUCOSE.  Covered  with  wart- 
like  prominences. 

VERTEBRA  (Lat.    verto,    I   turn). 


One  of  the  bones  of  the  spinal 
column  or  backbone. 

VERTICILLATE.    Placed  in  whirls. 

VESICLE  (Lat.  vesica,  a  bladder). 
A  little  sac,  bladder,  or  cyst. 

VISCERA  (Lat.  viscus).  The  inter- 
nal organs  of  the  body. 

VIVIPAROUS  (Lat.  mvus,  alive  ;  and 
pario,  I  bring  forth).  Applied  to 
animals  which  bring  forth  their 
young  alive. 

ZOOID  (Gr.  zoon,  animal ;  eidos, 
form).  The  highly  specialized 
organs  of  such  animals  as  the 
Hydroids,  and  other  compound 
forms  which  have  a  marked  in- 
dividuality, and  which  might  be 
mistaken  for  genuine  individu- 
als. 

ZOOPHYTE  (Gr.  zoon,  animal  ;  phu- 
ton,  .plant).  Applied  to  the 
plant-like  polyps,  sertularians, 
and  sponges. 


INDEX. 


ACANTHARCHUS  POMOTIS,  443 
Acanthocephali,  165,  175 
Acantlioglossus  Bruijnii,  573 
Acarina,  359,  386 
Acliorutes  nivicola,  364 
Acineta,  34 
Acipenser  sturio,  427 

development  of,  437 
Acrania,  401,  405 
Actheres  Carpenter!,  298 
Actinia,  74,  78 
Actinophrys  sol,  27 
Actinosphserium,  26 
Actinozoa,  74,  91 
Adaptation  of  animals  to  their  sur- 
roundings, 10 
Adder,  puff,  499 
JEgineta,  62 
^Bolis  pilata,  265 
^ZEpyornis,  538 
Agahnopsis,  70 
Agamogenesis,  54 
Agelacrinus,  108 
Ai,  579 

Aix  sponsa,  543 
Albatross,  542 
Albertia,  179 
Alca  impennis,  541 
Alcyonaria,  85,  91 
Alectorides,  544 
Aletia,  379 
Alewife,  450,  451 
Alligator  Mississippiensis,  514 
Alopecias  vulpes,  420 
Alosa  sapid  issima,  450 
Alpheus,  315 


Alytes  obstetricans,  484 
Amarcecium,  200 
Ambergris,  593 
Amblyopsis  spelseus,  453 
Amblyrhynclius,  504 
Amblystoma  mavortium,  479 
Amia  calva,  433 
Amiurus  lynx,  443 
Ammocoetes,  410 
Ammonites,  280 
Amoeba,  3,  17,  22 
Ampelis  cedrorum,  555 
Amphibia,  464 
Amphioxus,  structure  of,  406 

development  of,  407 
Amphipoda,  305 
Amphisbaena,  502,  503 
Amphitrite  cirrata,  236 

ornata,  239 

Ampullae  of  Echinoderms,  97 
Anabas  scandens,  457 
Anadromous  fishes,  451 
Analogy,  12 
Anas  boschas,  543 

obscura,  543 
Anchitherium,  602 
Ancistrodon  contortrix,  500 

piscivorus,  500 
Andrena,  384 
Andrias  Scheuchzeri,  479 
Anemone,  sea,  74 
Angle,  facial,  626 
Angler,  442,  460 
Anguilla  acutirostris,  446 
Anguillula  aceti,  170 

tritici,  170 


098 


INDEX. 


Animalcule,  bear,  361 
Animalcules,  bell,  39 

infusorian,  31 

root,  22 

trumpet,  35 
Animal  kingdom,  classification  of, 

15 
Animals,  development  of,  643 

distinguished  from  plants,  1 

nigh  and  low,  6 
Annelides,  229,  238 
Annulata,  characters  of,  225 

classification  of,  238 
Anochanus  sinensis,  121 
Anodonta,  245 
Anolis,  503 
Anomodontia,  512 
Anopla,  218 

Anoplodium  Schneideri,  145 
Ant,  381 

Ant-eater,  spiny,  573 
Ant,  white,  367 
Antedon  rosace  us,  105 
Antelope,  prong  horn,  609 
Anthracarida,  306 
Anthrapalaernon,  314 
Anthropoidea,  618,  619 
Antilocapra  Americana,  609 
Antipathes  arborea,  85 
Anura,  483,  488 
Apes,  621 
Aphis,  371,  653 

lion,  367 

Apis  mellifica,  385 
Aploceros  montanus,  610 
Apodes,  446 
Appendicularia.  199 
Apteryx,  538 
Aptornis,  538 
Apus  aequalis,  302 
Arachnactis,79 
Arachnida,  characters  of,  358,  386 

development  of,  362 
Araneina,  362,  386 
Arcella,  24 
Archseopteryx  macrura,  537 


Archaster,  114 
Ajchegosaurus,  482 
Architeuthis  monachus,  282 

princeps,  282 
Arciferous  Anura,  484 
Arcturus  Baffini,  310 
Argonauta,  283 
Argulus  alosse,  299 
Armadillo,  580 
Army  worm,  379 
Artemia  fertilis,  304 

gracilis,  303 
Arthromere,  286 
Arthropoda,  characters  of,  285 
Artiodactyla,  600,  605 
Ascaris  dentata,  164 

lumbricoides,  167 

mystax,  167 

nigrovenosa,  164 
Ascetta  primordialis,  42 
Ascidia  callosa,  202 

gigas,  202 
Ascidiacea,  197,  215 
Ascidiaus,  196 
Asellus,  308,  310 
Asexual  generation,  653 
Asiphonia,  256 
Asp,  499 

Aspergillum,  250 
Aspidogaster  conch  i  cola,  152 
Aspidonectes  spinifer,  510 
Aspredo,  449 

Asterias  vulgaris,  96,  112,  115 
Asteridea,  111,  116 
Asteroidea,  109,  116 
Astraea  pallida,  81 
Astrangia,  80 
Astrangia  Danae,  81 
Astrogonium,  114 
Astroides,  development  of,  82 
Astropecten,  114 
Astrophyton  Agassizii,  111 
Atalapha  noveboracensis,  591 
Ateles,  560,  620 
Atlantosaurus,  515 
Atoll,  89 


INDEX. 


699 


Atrium,  198 

Auk,  great,  541 

Aurelia  aurita,  63 
flavidula,  65 

Auricularia,  132 

Auroch,  612 

Autechinida,  123,  126 

Autolycus,  235 

Automata,  animals  as,  682 

Aves,  anatomy  of,  518,  525 
characters  of,  518,  557 
development  of,  532 
feathers  of,  523 
moulting  of,  534 
nesting  habits  of,  536 
sexual  colors  of,  535 
skeleton  of,  518,  519,  521 
songs  of,  535 
topography  of,  520 

Axinella  polypoides,  48 

Axolotl,  479 

Aye-aye,  619 

BABOON,  620 
Baleena  mysticetus,  592 
Balaeniceps  rex,  545 
Balaenoptera  boops,  592 
Balanoglossus  aurantiacus,  219 
Balanns  balanoides,  293 
Balatro,  179 
Baphetes,  483 
Barnacle,  292 

anatomy  of,  293 
Barramundi  fish,  430 
Bathycrinus,  101 
Bats,  588 
Batrachia,  breeding  habits  of,  484 

characters  of,  464,  487 

development  of,  476 

gills  of,  468 

poison  of,  475 

reproduction  of  lost  parts  of, 
481 

skeleton  of,  465 

teeth  of,  467 

viviparous,  479 


Bear,  615 
Beaver,  584 

^79,  385 
Be^    372 

oil,  372 

Belone  longirostrus,  454 
Bilateral  symmetry  of  Ctenophora, 
92,  93 

Echinoderms,  96,  120 
Bilharzia  haBmatobia,  152 
Bill  fish,  454 
Bimana,  624 

Bipalium  dendrophilus,  143 
Bipinnaria,  113 
Birds,  diving,  541 

of  prey,  548 

perching,  551 

raptorial,  548 

swimming,  543 

(Also  see  Aves.) 
Bison,  611 

Bladder,  swimming,  of  fishes,  442 
Blastoidea,  107,  109 
Blind  fish,  442,  444,  453 

shrimps,  315 
Blissus  leucopterus,  370 
Blister  beetles,  373 
Blood,  circulation  of,  635 
Blood  corpuscles,  8 
Blue-fish,  455 
Boa-constrictor,  496 
Bolina  alata,  92,  93 
Boltenia  reniformis,  anatomy  of, 

197 

Bonellia  viridis,  224 
Bootherium,  610 
Bopyrus  pandalicola,  308 
Bos  longifrons,  612 

primigenius,  612 

taurus,  613 
Bot  fly,  375 

Bothriocephalus  latus,  159 
Box-fish,  462 
Brachiata,  101,  109 
Brachiolaria,  113 
Brachionus,  development  of,  178 


700 


INDEX, 


Brachiopoda,.  development  of,  192 

structure  of,  188,192,  195 
Bracbypyge  carbonis,  314 
Bradypus  tridactylus,  579 
Brain  coral,  80 

Brancliinectes  Coloradensis,  303 
Branchioganoidei,  431 
Branchiopoda,  299,  325 
Branchipus,  303 
Branta  Canadensis,  544 

leucopsis,  544 
Bream,  455 
Brisinga,  114 
Bristle-tails,  364 
Bruta,  577,  629 
Bryozoa,  180 
Bubo  Virginianus,  549 
Buccinum  undatum,  268 
Bucephalus  cuculus,  150 
Budding  in  Ascidians,  202,  212 

Hydroids,  54 

Infusoria,  37 

Medusa,  60 

Polyps,  77,  82 

Starfish,  110 
Bufo  ictericus,  475 

lentiginosus,  485 
Bugs,  370 
Bustard,  546 
Butcher  bird,  555 
Butterfly,  377 
Buzzard,  turkey,  548 

CACHELOT,  593 
Caddis  fly,  367 
Caiman,  515 
Cayman,  515 
Calamoichthys,  431 
Calcispongiae,  46,  49 
Caligus  curtus,  299 
Callignathus  simus,  594 
Callorhynchus,  424 
Caloptenus  spretus,  328 

femur-rubrum,  328 
Calyptrsea  sinensis,  263 

striata,  263 


Camarasaurus,  515 
Cambarus  pellucidus,  315 
Camel,  614 
Canielus,  614 
Campanulariae,  61 
Campodea,  364 

Americana,  365 

Cookei,  365 
Cancer  irroratus,  313 
Canis  caribasus,  617 

domesticus,  617 

extrarius,  617 

familiaris,  616 

latrans,  617 

leporarius,  617 

molossus,  617 

sagax,  617 

vertagus,  617 

Canthocamptus  cavernarum,  297 
Capelin,  452 
Capybara,  586 
Carcharias  gangeticus,  421 
Card i urn  pygmseum,  development 

of,  253 

Cariacus  Virginianus,  609 
Caribou,  609 
Cariuatse,  541,  557 
Carneospongeae,  47,  49 
Carnivora,  614,  629 
Carp,  453 
Caryocystites,  108 
Caryophyllseus,  161, 162 
Cassowaries,  539 
Catarrhinae,  620 
Cat,  anatomy  of,  564 

civet,  617 

domestic,  617 
Cat-fish,  443 
Catenula  lemnae,  144 

quaterna,  144 
Cathartes  atratus,  548 

aura,  548 
Cattle  tick,  360 
Caudina  arenata,  134 
Cavolina  tridentata,  258 
Cebus,  620 


INDEX. 


701 


Cecidomyia,  377 
Cells,  5 

Centipede,  358 
Cephalaspis  Lyellii,  427 
Cephalization,  289,  314,  405 
Cephalophora,  characters  of,  2d7 

classification  of,  272 
Cephalopoda,  characters  of,  272 

classification  of,  283 

development  of,  278 
Cephalopterus  diabolus,  424 
Cephalula,  177 

of  worms,  233,  234 
Ceratodus  Fosteri,  429 
Cercaria  cystophora,  150 

echinata,  150 
Cercaria,  history  of,  147 
Cercoleptes,  615 
Cercopithecidse,  620 
Cerianthus  borealis,  79 
Cermatia  forceps,  358 
Cervus  Canadensis,  609 
Cestodes,  structure  of,  153,  163 
Cestracion,  416 
Cetacea,  591,  629 
Cete,  591,  629 
Cetiosaurus,  515 
Chaetoderma  nitidulum,  224 
Chsetognathi,  174,  175 
Chsetopoda,  236 
Chsetosoma,  170 
Chalinula  oculata,  48 
Chameleon,  503 
Charybdaea,  62 
Cheiromys,  619 
Chelifer,  362 
Chelonia,  anatomy  of,  505 

characters  of,  504,  517 
Chelydra  serpentina,  510 
Chick,  development  of,  646 
Chilichthys  turgidus,  462 
Chilognatha,  356,  385 
Chilomycterus  geometricus,  462 
Chilopoda,  358,  386 
Chimsera,  425 

plumbea,  425 


Chimpanzee,  622 

Chinch-bug,  370 

Chirodota  laeve,  134 

Chiroptera,  588,  629 

Chirotes,  502 

Chiton,  nervous  system  of,  268 

Chiton  ruber,  268 

Chondroganoidei,  427 

Chorda  dorsalis  of  Ascidians,  206 

Chordeiles  Virginianus,  551 

Chrysemys  picta,  anatomy  of,  506 

Chrysothrix,  620 

Chub,  453 

Chub  sucker,  443 

Chyle  of  polyps,  77 

Chyme  of  polyps,  75 

Cicada,  seventeen-year,  371 

Cidaris  nutrix,  122 

Ciliary  motion,  142 

Ciliata,  35,  40 

Cinclides,  75 

Cinura,  365 

Cirratulus  grandis,  236 

Cirripedia,  292,  325 

Cistenides  Gouldli,  236 

Cladocera,  299 

Cladodactyla  crocea,  133 

Clam,  anatomy  of,  242 

Clamatores,  552 

Classification,  13 

Clepsine,  embryology  of,  228 

Clidiophora  trilineata,  250 

Climbing  fish,  457 

Cliona  sulphurea,  49 

Clione  papillonacea,  259 

Clupea  harengus,  450 

Clymenella  torquata,  236 

Clypeaster,  123 

Coati,  615 

Cochineal  insect,  371 

Cod,  458 

Codosiga  pulcherrimus,  32 

Coecilia,  482 

Coelenterata,  51 

Coenosarc  of  coral  polyps,  85 

Coleoptera,  372,  386 


702 


INDEX. 


Collembola,  364 
Collosphoera  spinosa,  27 
Colobus,  621 
Coloration,  protective,  675 

of  snakes,  497 
Colossochelys,  511 
Commensals,  68,  459 
Comparative  anatomy,  631 
Complementary  males,  293 
Compsemys,  511 
Compsognathus,  516 
Condor,  548 

Condylura  cristata,  587 
Conger  oceanicus.  446 

young  of,  446 

Conjugation  in  Infusoria,  39 
Conurus  Carolinensis,  550 
Copperhead  snake,  500 
Corals,  deep  sea,  84 

development  of,  83 

fishery,  85 

polyps,  74 

rate  of  growth  of,  84 

reefs,  formation  of,'  86,  88 

tabulate,  58 
Corallium  rubrum,  85 
Cordylophora  lacustris,  57 
Coreus  tristis,  370 
Cormus,  181 
Coryne  mirabilis,  59 
Coryphsena,  455 
Coryphodon,  571,  601 
Cotton  worm,  379 
Cowry  money,  269 
Crane  fly,  377 
Cranes,  544 
Craniota,  401,  405 
Craspeda  of  polyps,  75 
Craw-fish,  315 
Cribella  sanguinolenta,  115 
Crinoidea,  101,  108 

development  of,  105 
Crocodilia,  514,  517 
Crocodilus  acutus,  514 
Crossaster  papposus,  115 


Crow,  carrion,  548 

Crustacea,  classification  of,  292, 325 
structure  of,  286 

Cryptobranchus  Japonicus,  479 

Cryptoccelum  opacum,  145 

Cryptophialus  minutus,  297 

Ctenophora,    bilateral    symmetry 

of,  92 

characters  of,  92,  94 
classification  of,  95 
digestive  cavity  of,  92,  93 
nervous  system  of,  92 
water-vascular  system  of,  92 

Cuculi,  551 

Cuma,  313 

Cumacea,  314 

Cunina  octonaria,  63 

Gunner,  anatomy  of,  434 

Curlew,  545 

Cuttle-fish,  273 

gigantic,  281 

Cyamus  ceti,  311 

Cyanea  arctica,  67 

Cyclocardia  novangliee,  249 

Cyclops  quadricornis,  297 

Cyclostomata,  401 

Cyclostomi,  409 

Cymothoa,  308 

Cynthia  pyriformis,  202 

Cyphonautes.  187 

Cyprsea  moneta,  269 

Cyprinus,  453 

Cypris,  299 

Cysticercus  cellulosse,  156 

Cystid,  181 

Cystidese,  108,  109 

Cytode,  6 

DACE,  453 

Dactylogyrus  amphibothrium,  153 

fallax,  153 
Daphnia,  299 
Darter,  456 

Dasypus  novem-cinctus,  580 
Date  shell,  250 


INDEX. 


703 


Decapoda,  312,  325 

Cephalopoda,  280 
Deer,  608 

Deltocyathus  Agassizii,  80 
Dendroccela,  145 
Dendrocrelum  lacteum,  141,  144 

percaecum,  142 
Dendroeca  virens,  555 
Dental ium,  257 
Desmosticha,  126 
Devil-fish,  424 
Diatryma,  540 
Dibranchiata,  280,  284 
Dicyema,  139 
Dicyemella,  140 
Dicynodon,  512 

tigriceps,  512 
Didelphia,  571,  628 
Didelphys  Virginiana,  575 
Didus  ineptus,  547 
Diemyctylus  viridescens,  481 
Differentiation,  6 
Digestion,  organs  of,  631 
Digestive  canal,  9 
Dimorphism,  654 
Dingo,  617 

Dinichthys  Torrelli,  431 
Dinornis  giganteus,  538 
Dinosauria,  515,  517 
Dinotherium,  599 
Diomedea  exulans,  542 

fuliginosa,  542 
Diploria  cerebriformis,  80 
Diplozoon  paradoxum,  152 
Dipnoi,  425,  426,  428 
Diptera,  375,  386 
Discina,  193 
Discophora,  62,  72 
Dispersal  of  animals,  660 
Distomum  crassum,  151 

development  of,  147 

heterophyes,  151 

lanceolatum,  151 

macrostomum,  152 

ophthalmobium,  151 
Distribution,  geographical,  658 


Dodo,  547 
Dog-fish,  420 

shark,  420 

Dog,  varieties  of,  617 
Doliolum,  201,  208 
Dolphin,  455 
Doris,  265 

Dorosoma  cepedianum,  443 
Dove,  547 
Drum-fish,  443 
Duck,  black,  543 

canvas  back,  543 

eider,  543 

summer,  543 
Dugong,  596 
Dysmorphosa,  60 

EAGLE,  bald-headed,  548 
Ear,  641  ;  of  clam,  245 

of  Crustacea,  291 
Ears  of  mammals,  563 
Earwig,  368 
Earthworm,  anatomy  of,  229 

embryology  of,  230 
Ecardines,  196 
Echeneis  remora,  454 
Echidna  hystrix,  573 
Echinarachnius  parma,  123 
Echinococcus,  159 
Echinoderes,  179 

Echinodermata,  blood  system  of, 
100,  130 

characters  of,  96 

direct  development  of,  114, 
121,  133 

"  heart  "  of,  100,  104 

metamorphoses  of,  106,  112, 
120 

nervous  system  of,  97,  104 

skeleton  of,  97,  118 

viviparous,  110,  121,  122 

water-vascular  system  of,  99, 

130 

Echinoidea,  117,  126 
Echinorhynchus  angustatus,  166 

claviceps,  166 


704 


INDEX. 


Echinorhynclius  gigas,  165 
Echinus,  117 

esculentus,  123 
Echiurus,  224 
Eciton,  383 
Ectoderm,  6 
Ectoprocta,  188 
Educabilia,  582,  591 
Edentata,  577,  629 
Edible  Holotlmrians,  135 

sea-urchin,  123 
Edwardsia,  78 
Eel,  breeding  habits  of,  446 

conger,  446 

sound  produced  by,  444 
Eel-pout,  458 
Eggs,  winter,  of  Crustacea,  300 

Planarians,  145 

Polyzoa,  187 

Rotatoria,  178 

Elasmobranchii,  characters  of,  414, 
463 

development  of,  418 

eyes  of,  417 

teeth  of,  416 
Elaps,  497,  678 
Elasmosaurus  platyurus,  513 
Electrical  eel,  450 

fish  of  the  Nile,  449 

ray,  422 
Elephant,  597 
Elephas,  597 

primigenius,  598 
Elk,  608 
Elytra,  372 
Embryology,  13,  643 
Encrinites,  101 
Encrinus  liliformis,  137 
Endocyst,  181 
Endoderm,  6 
Endostyle,  199 
Enneacanthus  obesus,  456 
Enopla,  219 
Enteropneusta,  development  of,  220 

structure  of,  219,  221 
Entomostraca,  297,  325 


Entoprocta,  188 
Eohippus,  602 
Epeira  vulgaris,  363 
Ephemera,  367 
Epigonichthys  cultellus,  408 
Epipodium  of  mollusks,  258 
Epistome  of  Polyzoa,  184 
Epistylis,  39 
Epithelium,  7 

Epizoanthus  Americanus,  79 
Equus  asinus,  605 

caballus,  races  of,  603 

hemionus,  604 

onager,  604 

Erimyzon  oblongum,  443 
Eretmocbelys  imbricata,  510 
Escharina,  186 
Estheria  Belfragei,  302 
Euchone  elegans,  236 
Euplectellum  aspergillum,  48 
Eupomotis  aureus,  455. 
Euproops  Danse,  322 
Eupyrgus,  128 
Eurypauropus,  358 
Eurystomeae,  94 
Eustrongylus  buteonis,  169 

chordeilis,  169 

gigas,  168 

papillosus,  169 
Evolution,  11 

Existence,  struggle  for,  673 
Eye,  640 

dorsal,  of  Mollusca,  257 
of  blind  craw-fish,  315 
of  Crustacea,  290 
of  mollusks,  274 

FASCIOLA  HEPATICUM,  150 
Fauna,  661 

chief  zoological,  666 
Favia,  80 
Feathers,  523 
Felis  concolor,  617 

domestica,  617 
Ferse,  614 
Fer-de-lance,  499 


INDEX. 


705 


Fertilization  of  egg,  644 

Fierasfer,  459 

Filaria  hematica,  170 
lentis,  170 
medinensis,  169 
sanguinis-hominis,  170 

Fishes,  see  Pisces. 

Fishes,  anatomy  of,  434 
bony,  434 
characters  of,  411 
climbing,  457 
development  of,  445 
Elasinobranch,  414 
fins  of,  411,  428 
ganoid,  425 
lateral  line  of,  442 
mucous  canal  of,  442 
respiration  of,  442 
sounds  produced  by,  442 
spiracle  of,  417 
teeth  of,  416,  442 
viviparous,  418, 444 

Fish-hawk,  548 

Fish-lice,  297 

Fission  in  Planarians,  144 

Flabellum  angulare,  80 

Flagellata,  31,  40 

Flamingo,  544 

Flea,  377 

sand,  311,  376 
snow,  364 
water,  299 

Flounder,  459      , 

Fluke- worms,  147 

Fly,  bot,  375 

house,  374,  375 

Flying-fish,  453 

Foraminifera,  24,  27 

Forficula,  368 

Fossil  jelly-fishes,  71 
sea-urchins,  125 
star-fishes,  116 

Frog,  487 

anatomy  of,  470 

Fuligula  vallisneria,  543 

Fungia,  82 


GUDUS  MORRHUA,  458 
Galago,  619 

Galeopithecus  volans,  588 
Gall-flies,  two- winged,  377 
Gall-fly,  hymenopterous,  380 
Gallinago  Wilsonii,  545 
Gallinula,  544,  545 
Gammarus  robustus,  311 
Gampsonyx,  306 
Ganglion,  8 
Ganocephala,  482 
Ganoidei,  characters  of,  425,  463 

development  of,  432 
Gare  fowl,  541 
Gar-pike,  431 

development  of,  432 
Gasterosteus,  456 
Gastraeades,  140 
Gastropoda,  259,  272 
Gastrotheca,  485 
Gastrotricha,  179 
Gastrula,  43 
Gavial,  514 
Generations,  alternation  of,  652 

in  Ascidians,  210 

in  corals,  82 

in  Trematodes,  147 

in  worms,  235 

Geographical  distribution,  658 
Geological  succession,  668 
Geophilus  bipuncticeps,  358 
Geoplana  flava,  142 
Gephyrea,  development  of,  223 

structure  of,  221,  225 
Gerardia,  85 
Germigene,  141,  147 
Geryonia,  62 
Giant  bird,  545 
Gibbon,  621 
Gills,  637 
Gizzard-shad,  443 
Gland,  green,  of  lobster,  291 
Glass-snake,  Opheosaurus,  503 
Glires,  582,  629 
Globe-fish,  463 
Globicephalus  brachypterus,  595 


706 


INDEX. 


Globicephalus  melas,  595 
Globigerina  bulloides,  24 
Glycimeris  siliqua,  250 
Gljptodon,  580 
Gnathostomata,  401 
Gonotheca,  61 
Goose,  barnacle,  544 

wild,  544 
Goose-fish,  460 
Gordiacea,  171 
Gordius  aquaticus,  172 
Gorgonia  flabellum,  86 
Gorgonidse,  86 
Gorilla,  623 
Grallatores,  544 
Grampus  griseus,  595 
Graptolites,  61,  71 
Grasshopper,  anatomy  of,  328 
Gregarina  gigantea,  28 
Gregarinida,  28,  31 
Grilse,  452 
Guanin,  75 
Guillemot,  541 
Guinea-hen,  546 
Guyuia  annulata,  84 
Gymnarchus  niloticus,  449 
Gymnolsemata,  186 
Gymnomonera,  22 
Gymnophiona,  481,  488 
Gymnotus  electricus,  450 
Gynaecophore  of  trematode  worms 

152 
Gyrodactylus  elegans,  153 

HADROSA.UKUS,  515 
Hag-fish,  409 
Haimea,  85 
Hair,  561 
Hair-worms,  171 
Hake,  458 

Halcampa  producta,  78 
Haliaetus  leucocephalus,  548 
Halicore,  596 
Halistemma  carum,  70 
Halophila  borealis,  180 
Halyclystus  auricula,  64 


Haplodon  rufus,  585 
Haplophyllia  paradoxa,  84 
Hare,  varying,  586 
Harmony    between    animals    and 

their  surroundings,  675 
Harvest  men,  362 
Hatteria,  511 
Hearing,   organs  of,  in  mollusks, 

270 

Heliopora  coerulea,  85 
Heliozoa,  27 

Helix  albolabris,  anatomy  of,  265 
Hell-bender,  479 
Heloderma  horridum,  504 

suspectum,  504 
Hemiaster  cavernosus,  121 

Philippii,  121 
Hemippus,  604 
Hemiptera,  370,  386 
Herring,  450 
Hesperornis,  538 
Hessian  fly,  377 
Heterometabola,  364 
Heteromita,  33 
Heterodontidse,  416 
Heteropoda,  270,  273 
Hexapoda,  363,  386 
Hexathyridium  pinguicola,  152 

venarum,  152 

Himantopus  nigricollis,  545 
Hipparion,  602 
Hippocampus,  443 
Hippocampus  minor,  618 
Hippopotamus,  605 
Hirudinea,  development  of,  229 

structure  of,  226,  238 
Hoasin,  547 

Holocephali,  characters  of,  424 
Holopus,  104 
Holothuria  edulis,  135 

Floridana,  anatomy  of,  131 
Holothuroidea,  126,  136 
Homology,  12 
Homo  sapiens,  624 
Horned  toad,  503 
Horn-tail,  380 


INDEX. 


707 


Horse,  genealogy  of,  602 
races  of,  604 

House-fly,  374 

Humming-bird,  551 

Hyalonema  boreale,  48 

Hybocodon,  60 

Hybrid  ducks,  543 

Hybridity,  657 

Hydatids,  158 

Hydra,  anatomy  of,  52 

development  of,  56 
vulgaris,  52 

Hydractinia  echinata,  56 

Hydroidea,  52,  72 

Hydrozoa,  52,  71 

classification  of,  73 
nervous  system  of,  62,  65 
organs  of  taste  in,  63 

Hyla  Pickeringii,  484 

Hylobates,  622 

Hylodes  Martinicensis,  485 

Hymenoptera,  379,  387 

Hyocriiius,  102 

Hyoganoidei,  431 

Hyperia,  68,  311 

Hyperoartia,  410 

Hyperotetra,  410 

Hypobytliius  calycodes,  202 

Hypodermis,  289 

Hyracoidea,  599,  629 

Hyrax,  599 

IBLA,  293 

Ichneumon  fly,  381 

Ichtliyopterygia,  511,  517 

Iclithyornis,  538 

Ichthyosaur,  512 

Idotaea,  nervous    system  o2,  306, 

310 

Idyia  roseola,  93 
Iguana,  504 
Iguanodon,  515 
Individuality,  656 
Ineducabilia,  582 
Infusoria,  31,  40 
Inheritance,  law  of,  11 


Insectivora,  587,  629 

Insects,  anatomy  of,  328 
brain  of,  339 
characters  of,  327 
classification  of,  385 
digestion  in,  336 
ears  of,  345 
eye  of,  345 
embryology  of,  349 
locomotion  in,  347 
metamorphosis  of,  328 
parthenogenesis  in,  353 
polymorphism  in,  368 
respiration  of,  343 
senses  of,  346 
useful,  354 

Instinct,  nature  of,  680 

Isopoda, 305 

Isurus  punctatus,  420 

Ixodes  albipictus,  359 
bovis,  360 

JACCHUS,  620 
Jaws,  631 
Jelly-fish,  62 
Julus,  356 

KANGABOO,  575,  577 
Katydid,  676 
Killer-whale,  595 
King-bird,  552 
King-crab,  317 
Kinglet,  555 
Kiwi-kiwi,  538 
Kogia  Floweri,  594 

LABYRINTHICI,  457 
Labyrinthodou,  482,  483 
Labyrinthodontia,  482 
Lacertilia,  501,517 
Lachnosterna  fusca,  372 
Lactophrys  trigonus,  462 
Lselaps,  515 

Lagopus  leucurus,  546,  547 
Lamelli  branch! ata,  242 

classification  of,  256 


708 


INDEX. 


Lampreys,  409 

Lamp  shells,  188 

Lancelot,  406 

Larva  of  Echinoderms,     96,  105, 

110,  112, 120 
Hydrozoa,  83 
Insects,  328 
Worms,  232 
Lasso-cells  in  Aurelia,  67 

Hydra,  53 

Infusoria,  37 

Polyps,  76,  81 

Sponges,  43 

Worms,  143 

Lateral  line  of  fishes,  442 
Leaf  insect,  677 
Leech,  226 
Lemnisci,  165 
Lemur,  618 
Lepas  fascicularis,  293 
Lepidoptera,  377,  387 
Lepidosiren  paradoxa,  430 
Lepidosteus,  development  of,  432 
osseus,  431 
platystomus,  432 
spatula,  432 
Lepidurus  Couesii,  302 
Lepomonera,  22 
Leptocardii,  406,  408 
Leptocephalus,  446 
Leptodiscus  medusoides,  34 
Leptoplana,  144 
Leptosynapta  Girardii,  134 
Leptychaster,  114 
Lepus  Americanus,  586 

Bairdii,  586 

Lernaea  branchialis,  297 
Lerneonema  radiata,  298 
Leucochloridium,  152 
Lice,  plant,  371 
Ligula  simplicissima,  162 
Limacina  arctica,  258 
Limax  flavus,  265 
Limicolse,  544 
Limnadia  Agassizii,  302 
Limnetis  Gouldii,  301,  302 


Limnoria  terebrans,  310 

Limpet,  268 

Limulus,  anatomy  of,  317 

development  of,  320 

Polyphemus,  317 
Lineus,  218 
Lingual  ribbon  of  mollusks,  276, 

632 

Linguatulina,  361 
Lingula,  189,  190,  191 

pyramidata,  195 
Liodon,  500 

Lissotriton  punctatus,  481 
Lithobius  Americanus,  358 
Lithodomus,  250 
Littorina  littorea,  268 
Liver  fluke,  150 
Lizards,  sea,  504 

structure  of,  501 
Lobatae,  95 

Lobster,  anatomy  of,  286 
Locust,  anatomy  of,  328 
Loggerhead  turtle,  510 
Loligo  pallida,  273 

Pealii,  anatomy  of,  273 
Loon,  541 

Lophius  piscatorius,  460 
Lophobranchii,  460 
Lophohelia  prolifera,  80 
Lophophore,  182 
Loxosoma,  185,  187 
Lucernaria,  63 
Lucifuga  subterraneus,  459 
Luidia,  114 
Lumbricus  agricola,  230 

rubellus,  230 

terrestris,  229 

Lunatia  heros,  anatomy  of,  261 
Lung-fish,  428 
Lyinnaeua  appressus,  266 

elodes,  266 
Lymphatics,  636 
Lynx  Canadensis,  617 

rufus,  617 
Lyre-bird,  552 
Lystrosaurus,  513 


INDEX. 


709 


Lytta  marginata,  373 

MACACUS,  620 

Machilis,  365 

Mackerel,  456 

Macrobiotus  Americanus,  361 

Macropus  thetidis,  577 

Mactra  lateralis,  249 

ovalis,  251 

Madrepora  cervicornis,  82 
Ma?andrina,  80, 81,  84 
Magpie,  554 
Malacopoda,  355,  385 
Malapterurus  electricus,  449 
Male  fishes,  obstetrical  habits  of, 

449,  461 

Mallotus  villosus,  452 
Mammalia,  anatomy  of,  564 
characters  of,  557,  628 
development  of,  566 
ears  of.  563 
hair  of,  561 
horns  of,  561 
limbs  of,  560 
music  of,  569 
sexual  differences  of,  566 
skeleton  of,  558 
teeth  of,  562 

Mammals,  development  of,  649 
Mammoth,  598 
Man,  embryology  of,  650 
origin  of,  627 
relation  to  apes,  624 
skull,  626 
varieties  of,  627 
Manatus,  595 
Mandrill,  620 
Manis,  580 
Mantis,  369 
Manubrium,  70 
Marine    animals,  distribution  of 

664 

Marmoset,  619 
Mar supi alia,  574 

Marsipobranchii,     characters    of 
409,  410 


Mastodon  giganteum,  599 
May  fly,  367 
Meckelia  ingens,  218 
Medusa,  59 
Megalops,  313 
Megapodius,  546 
Megatherium,  579 
Melanogrammus  seglefinus,  458 
Melipona,  385 
Mellita  testudinata,  123 
Meloe  angusticollis,  373 
Melospiza,  555 
Membranipora  pilosa,  186 

solida,  180 
Memory  of  animals,  681 
Menhaden,  450 
Menobranchus,  478 
Menopoma  Alleghaniensis,  479 
Merostomata,  317,  326 
Mesenteries  of  polyps,  75 
Mesoderm,  6 

Mesogonistius  chsetodon,  455 

Mesohippus,  602 

Mesozoa,  139 

Metabola,  364 

Metamorphosis,  651 

cf  Batrachia,  476 

suppressed,  477,  485 

of  Crustacea,  313 

of  echinoderms,  105, 110, 112 

Metridium  marginatum,  74 

Miastor,  653 

Microsauria,  482,  483 

Microstomum  lineare,  strobilation 
in,  145 

Midas,  620 

Migrations  of  animals,  667 

Millepedes,  356 

Millepora  alcicornis,  57 
nodosa,  57 

Milnesium  tardigradum,  361 

Mimicry,  protective,  675 

Mimetes  niger,  622 
pithecus,  621 

Mind,  in  animals,  682 

Miohippus,  602 


710 


INDEX. 


Mites,  359 

Moa,  538 

Moccasin  snake,  500 

MolacantlmsPallasii,  463 

Mola  rotunda,  462 

Mole,  587 

Molgula,  197 

Mollusca,  development  of,  253,  263 

structure  of,  240 
Molluscs,  edible,  268 
Monads,  31 
Monas  termo,  31 
Monera,  18,  20 
Money,  shells  used  as,  269 
Monitor,  504 
Monkey,  619 
Monocaulus,  60 
Monodelphia,  571,  577,  629 
Monodon  monoceros,  594 
Monograptus,  G2 

Monostomum,  development  of,  149 
Monotremes,  571 
Morphology,  5 
Morula,  43 

Mosasaurus  maximus,  500 
Mosquito,  377 
Moths,  378 
Mound  bird,  546 
Mouse,  586 

Mucous  canal  of  fishes,  442 
Mud  dauber,  383 
Mud  fish,  432 

puppy,  478 

sun  fish,  443 
Mullet,  443 
Mus,  586 

Musca  domestica,  375 
Musical  fishes,  443 
Music  of  mammals,  569 
Mussa,  80 
Mussel,  edible,  248 

development  of,  254 
Mustela  foina,  617 
Mustelus  canis,  420 

laevis,  420 

vulgar! s,  420 


Muzir,  604 

Mya  arenaria,  242 

My  gale  avicularia,  363 

Hentzii,  36& 
Myliobatis,  416, 424 

fremenvillii,  422 
Mylodon,  579 
Myriopoda,  356,  385 
Myriotrochus  Rinkii,  134 
Myriozoum  subgracile,  180 
Mysis,  313 
Mysticete,  592 
Mytilus  edulis,  248 
Myxine,  409 

NAJA,  499 

Nanemys  guttatus.  510 

Narwhale,  594 

Nasua,  615 

Natatores,  544 

Natica  heros,  anatomy  of,  261 

Natrix  torquata,  495 

Nauplius,  294 

Nautilus  pompilius,  280 

Nebalia,  311 

bipes,  312 

Necturus  lateralis,  478 
Nematelminthfs,   development  of, 
164 

structure  of,  163,  175 
Nematodes,  167, 175 
Nematogene,  141 
Nemertian  worms,  216 
Nemertina,  development  of,  217 

structure  of,  216,  219 
Neocarida,  292, 325 
Neochanna,  452 
Nephila  plumipes,  363 
Nereis  virens,  anatomy  of,  231 
Nervous  system,  638 
Nervous  system,  of  ctenophores,  92 

liydrozoa,  62,  65 
Nests  of  birds,  536 
Neuroptera,  365,  386 
Neurula  stage  of  leeches,  228 

worms,  230 


INDEX. 


711 


Nightliawk,  551 

Noctiluca  miliaris,  33 

Noises  produced  by  fishes,  442,  443 

Notacanthus,  446 

Notocliord  of  ascidians,  206 

Notommata,  177 

Nototrema  marsupiatum,  485 

Nudibranch  molluscs,  265 

Nuraerius  longirostris,  545 

Nummulites,  25 

Nurse  of  trematode  worms,  149 

Nyctea  nivea,  549 

OCULINA,  80 
Octacnemus  bytliius,  202 
Octopod  cephalopoda,  280 
Octopus  Bairdii,  282 

punctatus,  283 
Odontopliore,  276 
Odontornithes,  537,  557 
(Ecodoma,  382 
Oligochaeta,  236 
Onchidium,  257 
Oniscus  murarius,  307 
Operculurn  of  gastropoda,  261 
Ophidia,  496,  517 
Ophiocoma  vivipara,  110 
Ophiopholisbellis,  110 
Opliiuridea,  109,  116 
Opisthodelphys  ovifera,  485 
Opistliomi,  446 
Opossum,  575 
Orang,  622 
Orca  gladiator,  595 
Oreortyx  pictus,  546 
Organisms,  6,  23 
Organs,comparative  anatomy  of ,631 

of  circulation,  635 

of  digestion,  631 

of  respiration,  637 

of  sense,  640 

of  smell,  642 

nature  of,  4,  6,  8,  9 
Origin  of  species,  671 
Ornitliodelphia,  571,  628 
Ornithosauria,  516 


Oroliippus,  602 
Ortliagoriscus  oblongus,  462 
Orthoptera,  368,  386 
Oscines,  552,  553 
Oscula  of  sponges,  43 
Osmerus  eperlanus,  452 

mordax,  452 
Osprey,  548 
Ostracoda,  299 
Ostrich,  539 
Otocyst,  270,  641 

of  clam,  245 

of  worms,  143 
Ova,  winter,  of  planarians,  145 

of  polyzoa,  187 

of  Rotator!  a,  178 
Ovibos  moschatus,  610 

priscus,  610 
Ovis  argali,  610 

aries,  610 

montana,  610 
Owl,  548 
Ox,  612 

Oxyuris  vermicularis,  167 
Oyster,  pearl,  252 

PADDLE  FISH,  427 
Palseocarida,  292,  315,  326 
Palaeontology,  16 
Palamedea  cornuta,  546 
Palapteryx,  538 
Palechinida,  123,  126 
Palisade  worm,  168 
Paludicella,  182 
Pandion  haliaetus,  548 
Pangolin,  580 
Panopaea  arctica,  250 
Paragorgia  arborea,  86 
Paramecium  caudatum,  35 
Parr,  452 
Parroquet,  550 
Parrot,  550 
Parthenogenesis,  54,  652 

in  ascidians,  213 
Partridge,  546 
Passeres,  551 


712 


INDEX. 


Patella  vulgata,  268 
Pauropoda,  356,  386 
Pauropus  Lubbockii,  356 
Pearl  oyster,  252 

shell,  252 
Pedicellaria,  97 
Pediculati,  460 
Podipalpi,  362,  386 
Pelagic  moll  uses,  258,  269 
Pelecanus  erythrorhynchus,  535 
Pelican,  542 
Pelobates,  484 

Pelodytes  (a  genus  of  frogs),  484 
(a  genus  of  thread  worms), 

164 

Pelomyxa  palustris,  24 
Pelopseus,  383 
Peltogaster,  296,  297 
Pelycosauria,  512 
Peuella,  298 
Penguin,  541 
Pennatula  aculeata,  86 
Pentacrinus,  101 

Pentacta  frondosa,  anatomy  of,  127 
Pentastoma,  361 
Pentremites,  107 
Perca  fluviatilis,  455 
Perch,  455 

sea,  anatomy  of,  434 
Peridinium,  34 
Peripatus,  anatomy  of,  355 
Perisarc,  61 
Perissodactyla,  600 
Perla,  367 
Perophora,  201 
Petalosticha,  123,  126 
Petromyzon  mariuus,  410 
niger,  410 
nigrieans,  410 
Pezopliaps  solitarius,  547 
Phalangella  flabellans,  186 
Phalangium,  362 
Pharyngobranchii,  408 
Phascolosoma  caemeatarium,  224 

Gould ii,  222 
Pheronema  Anme,  48 


Phocaena  brachycium,  595 

lineata,  595 

Phoenicopterus  ruber,  544 
Phoronis,  223 

Phosphorescent  annelides,  237 
ascidians,  202 
Hydrozoa,  70 
insects,  375 
Protozoa,  33 
worms,  237 

Phrynosoma  Douglassii,  503 
Phylactolsemata,  186 
Phyllocarida,  311,  325 
Phyllopoda,  300 
Physa  heterostropha,  265 
Physalia  aretlmsa,  68 
Physeter  macrocephalus,  594 
Physiology,  12 
Picarise,  550 
Pigeon,  anatomy  of,  525 
Pilidium,  217 
Pill  bug,  306,  307 
Pipa  Americana,  485 
Pipe  fish,  461 
Pirarucu,  442 
Pisces,  characters  of,  411,  463 

development  of,  413, 432, 445 
Pissodes  strobi,  372 
Plagiostomi,  419 
Plagusia,  460 
Planarian  worms,  141 
land,  145 
lasso-  cells  of,  143 
nervous  system  of,  143 
parasitic,  145 
Planaria  torva,  141 
Plant  lice,  371 
Planula,  59 
PJatygaster,  381 
Platyhelminthes,  141,  162 
Platyrhinse,  619 
Plectognathi,  461 
Pliohippus,  602 
Plesiosaurus,  513 
Plethodon  erythronotum,  479 
Plcurobrachia  rliododactyla,  93 


INDEX. 


713 


Pleurolepig  pellucidus,  456 
Pleuroma,  298 
Pleurum  of  insects,  329 
Pluniatella,  182 
Pneumophora,  134 
Podura,  364 
Pogouias  cliromis,  443 
Pogy,  450 
Poisonous  batrachians,  475 

jelly  fish,  67 

siplionopliores,  68 

snakes,  497,  499 
Polycelis,  144 
Polycladus  Gayi,  143 
Polydora,  development  of,  233 
Polykrikos,  37 
Polymorphism,  654 

in  insects,  368 
Polyodou  folium,  428 
Polypedates,  484 
Polypide,  181 
Polyps,  coral,  74 
Polypterus  bicliir,  431 

Senegalus,  431 
Polystomeae,  152 
Polystomum  integerrimum,  153 
Polyzoa,  development  of,  185 

structure  of,  180, 188 
Polyzoarium,  181 
Pomatomus  saltatrix,  455 
Pomolobus  pseudoliarengus,  450 
Pomotis,  455 
Porcellio,  306,  310 
Porcupine  fish,  462 
Porifera,  42, 49 
Porphyrio  coerulescens,  545 
Porpoise,  595 
Porsana  Carolina,  544 
Portuguese  man-of-war,  69 
Potamotrygon,  424 
Pourtalesia,  124 
Prestwi cliia  rotund atus,  322 
Primates,  618,  629 
Primnoa  reseda,  86 
Pristis  antiquorum,  421 
Perrotcli,  421 


Proboscidea,  597,  629 

Procyon  lotor,  615 

Proglottis  of  tape  woims,  156 
trematode  worms,  150 

Prorbynchus,  216 

Proscolex  of  tape  worms,  156 
trematode  worms,  150 

Prosimia?,  618 

Protamceba,  19 

Protaster,  111 

Protective  resemblance,  487,  675 

Proteida,  478,  488 

Proteus,  478 

Protista,  2 

Protoliippus,  602 

Protomonas  amyli,  19 

Protomyxa,  19 

Protomyxa  aurantiaca,  19 

Protoplasm,  5 

Protoplasta,  31 

Protopterus  annectens,  430 

Protozoa,  17,  41 

contractile  vesicles  of,  32 

Pseudes  paradoxa,  487 

Pseudobranclius  striatus,  478 

Pseudocrinus,  108 

Pseudofilaria,  young  of  gregariua, 

30 

Pseudemys,  510 
Pseudopleuronectes     Americanus, 

460 

Pseudopodia,  23 
Pseudopus,  502 
Psolus  epbippifer,  133 
Psycliology,  12 
Ptarmigan,  546 
Pteranodou,  517 
Pteraster,  114 
Pterodactyle,  516 
Pteropoda,  258,  272 
Pterosauria,  516,  517 
Pterotracliea  coronata,  271 
Ptyelus  lineatus,  371 
Puffer  fish,  462 
Pulex  irritans,  376 
Pulmonata,  265 


714 


INDEX. 


Pupa  of  insects,  328 

of  the  barnacle,  296 
Purpura  lapillus,  263 
Pycnogonidse,  360 
Pycnopodia,  115 
Pygidium,  324 
Pyrosoma  gigas,  202 
Pythonoinorpha,  500,  517 

QUOHOG,  249 

RACCOON,  615 
Radiolaria,  26,  27 
Rail,  544 
Raja  eglanteria,  422 

erinacea,  421 

fluviatilis,  424 

Isevis,  421 
Rana,  487 

halecina,  470 
Rangifer  caribou,  609 

tarandus,  609 
Raptores,  548 
Rasores,  546 
Rat,  black,  586 

blind,  586 
Ratitse,  538,  557 
Rattlesnake,  499 
Ray,  421 

sting,  424 

Reasoning  power  of  animals,  380 
Redia  of  trematodes,  150,  151 
Reefs,  coral,  formation  of,  87 
Reindeer,  609 
Renilla  reniformis,  86 
Reproduction,  13,  643 
Reproduction  of  lost  parts  in  Hy- 
drozoa,  53 

planarians,  144 
Reproduction  of  lost  parts  in  Ba- 

trachia,  481 
Reptilia,  characters  of,  488, 517 

development  of,  495 

skeleton  of,  489 

sexual  differences  of,  494 

teeth  of,  491,  499 


Reptilia,  viviparous,  495,  497 
Resemblance,  protective,  487,  575 
Respiration,  organs  of,  637 
Rhabdocoela,  145 
Rhabdopleura  mirabilis,  187 
Ramphorynchus,  517 
Rhea  Americana,  539 
Rhinichthys  atronasus,  453 
Rhizocrinus  lofotensis,  102 
Rhizopoda,  22,  27 
Rhombogene,  141 
Rhopalodina,  132 
Rhynchocephalia,  511,  517 
Rhyncodesmus  sylvaticus,  145 
Rhytina  Stelleri,  596 
Robin,  556 
Rodentia,  582,  629 
Root  barnacle,  296 
Rotalia,  25 
Rotatoria,  development  of,  178 

structure  of,  176,  180 
Rotifera,  176 
Rotifer  vulgaris,  176 
Rugose  corals,  84 
Ruminantia,  605 

SACCATE,  95 
Sacculina,  296 
Sagitta,  174 
Salamander,  479 
Salenoglyph  snakes,  499 
Sal  mo  fontinalis,  452 

quinnat,  451 

salar,  452 
Salmon,  451 
Salpa,  development  of,  211,  214 

structure  of,  201,  208 

spinosa,  211 

Sarcorhamphus  gryplms,  548 
Sauropterygia,  513,  517 
Sauropsida,  518 
Saururse,  537,  557 
Saw  fish,  421 
Saw  fly,  380 
Saxicava,  250 
Scalpellum,  293 


INDEX. 


715 


Scaphiopus,  484 
Scaphirhynchops    platyrhynclius, 

427 

Scapliopoda,  257,  272 
Sceleporus  undulatus,  anatomy  of, 

493,  504 

Schizaster  fragilis,  124 
Scbizopoda,  314 
Scolex  of  tape  worms,  156 

trematode  worms,  150 
Scolopendra  gigantea,  358 

lieros,  358 
Scolopeudrella,  358 
Scomber  scombrus,  456 
Scjphophori,  449 
Seal,  614 
Sea-anemone,  74 
Sea-cow,  595 
Sea-cucumber,  anatomy  of,  128 

apodous,  133 

pedate,  133,  135 
Sea-fan  corals,  86 
Sea-liorse,  443 
Sea-lion,  614 
Sea-pen,  86 
Sea-squirts,  196 
Sea-worms,  231 
Selache  maxima,  420 
Selachians,  414 
Semotilus  rliotlieus,  453 
Senmopithecus,  621 
Sense,  organs  of,  640 
Serolis  Gaudickaudi,  306 
Sertularia,  61 
Sewellel,  585 

Sexual  coloration  in  fisbes,  444 
Shad,  450,  451 

gizzard,  443 
Shagreen,  415 
Shark,  basking,  420 

hammer-headed,  421 

mackerel,  419 

Port  Jackson,  416 

thresber,  420 
Sharks,  414 
Sheep,  varieties  of,  609 


Sheep,  musk,  610 
Sheep  bydatid,  160 
Shells,  fossil,  270 
Ship  worm,  250,254 
Showt'l,  585 
Shrew,  587 
Shrike,  555 
Shrimp,  312,  314 
Sida,  299 
Simiae,  619 
Siphoniata,  256 
Siphonophora,  68,  72 
Siphonops,  482 
Siphydora  echinoides,  47 
Sipunculus,  221,  224 
Siredon,  479 
Sirenia,  595,  629 
Siren  lacertina,  478 
Sivatherium,  605 
Skates,  421 

development  of,  419 
Skull,  brachycephalic,  627 

dolicocephalic,  627 
Slug,  265 
Smelt,  452 
Smolt,  452 
Smynthurus,  364 
Snail,  265 
Snake,  hooded,  499 

striped,  anatomy  of,  498 
Snakes,  496 

protective  coloration  of,  497 

viviparous,  497 
Snipe,  545 
Snow-flea,  364 
Solaster  endeca,  115 
Solitaire,  547 

Somateria  inollissima,  543 
Somite,  286 
Sorex  platyrhinus,  587 
Sounds  produced  by  insects,  369 
Sounds,  fishes',  442 
Spalax,  586 
Sparrow,  555 
Spatangus,  124 
Specialization,  6 


716 


INDEX. 


Species,  origin  of,  672 

variation  of,  10,  672,  673 
Spermaceti,  593 
Spermatozoa,  formation  of,  644 
Sphaerodorum  231 
Sphargis  coriacea,  510 
Splienodon,  511 
Splieotyto  cunicularia,  549 
Spliex  iclmeumonea,  383 
Sphinx,  379 
Spiders,  362 
Spirialis  Gouldii,  259 
Spirula  Peronii,  281 
Spliyrna  zygaena,  421 
Spirorbis,  237 
Spirostreplion  Copei,  356 
Sponges,  42 

useful,  49 
Spongia  adriatica,  49 

equina,  49 

gossypina,  49 

tubulifera,  49 
Spongilla,  47 
Spoonbill  fish,  428 
Sporocyst  of  Nematodes,  151 
Spring-tails,  364 
Squalus  Americanus,  420 
Squamella  oblonga,  176 
Squid,  anatomy  of,  273 
Squilla,  312 
Squirrels,  flying,  583 
Star  fish,  96, 109,  111 

anatomy  of,  96 
Star  worm,  221 
Statoblast,  187 
Stegocephala,  482,  488 
Steller's  manatee,  596 
Stentor  polyrnorphus,  36 
Sternum  of  insects,  329 
Stick  insect,  677 
Stickleback,  456 
Stilt,  546 
Sting  rays,  424 
Stomapoda,  312,  325 
Stone  lilies,  101 
Strobila  of  Hydrozoa,  66 


Strobila  of  planarians,  144 

tape  worms,  156 
Strobilation   in   worms,  144,    145, 

234 

Struggle  for  existence,  673 
Struthio  camelus,  539 
Sturgeon,  embryology  of,  427 
Sturgeon,  427 
Stygicola  dentata,  459 
Stylaster,  58 
Styliola  vitrea,  258 
Styloclms  elliptica,  144 
Stylocordyla,  48 
Stylops,  373,  374 
Sucker,  453,  454 
Suctoria,  40 
Sun  fish,  fresh  water,  455 

banded,  455 

spotted,  456 

salt  water,  4G2 
Swimming,  in  fishes,  444 
Sycandra,  44 
Sycon  ciliatum,  45 
Syllis,  235 

Symmetry,     bilateral,    in    cteno- 
phores,  92,  93 

echinoderms,  120 
Synapta,  134,  135 
Syngnathus  peckianus,  461 
Synthetic  types,  483,  679 
Syrinx,  526,  552 
Syrnium  cinereum,  549 
Syrphus,  375 

TABULATE  CORALS,  58 

Tachiua,  375 

Taenia  acanthotrias,  157 

bacillaris,  155 

coenurus,  160,  161 

echinococcus,  158 

mediocanellata,  158 

solium,  155,  157 
Taeniata,  95 
Tape  worms,  development  of,  154 

structure  of,  153 
Tardigrades,  361 


INDEX. 


717 


Tarpau,  604 
Tasmanian  devil,  575 

wolf,  575 
Taste,  organs  of,  in  Hydrozoa,  63 

insects,  346 

polyps,  77 
Tautogolabrus  adspersus,  anatomy 

of,  434 
Teeth,  631 

rudimentary,  402 

of  sea-urchins,  118 
Teleocephali,  449 
Teleostei,  characters  of,  434,  464 

anatomy  of,  434 
Tentaculifera,  34,  40 
Teratology,  646 
Terebratulina  septentrionalis,  188 

development  of,  192 
Terebrella,  236 
Teredo  navalis,  250 
Tergipes  lacinulata,  265 
Tergum  of  insects,  329 
Termes  bellicosus,  368 

flavipes,  367 
Terrapin,  510 
Testicardines,  196 
Testudo  Indica,  510 
Tetrabranchiata,  280,  284 
Tetradecapoda,  305,  325 
Tetrajo,  546 
Tetrarhynchus,  162 
Tetrastemina  serpentinum,  219 
Tetrastoma  renale,  152 
Tetrodon  laevigatus,  462 
Thalascaris,  315 
Thalassochelys  caouana,  510 
Thaliacea,  208,  215 
Thamnocephalus  brachyurus,  303 
Theca  of  corals,  79 
Thelyphonus  giganteus,  362 
Theriodonts,  513 
Theromorpha,  512,  517 
Thrasher  whale,  595 
Thrips,  370 
Thylacinus,  575 
Thyone  briareus,  anatomy  of,  131 


Thysanura,  364,  386 
Tick,  359 
Tinamous,  547 
Tipula,  377 
Tissues,  6,  7 
Tissue,  bony,  8 

cartilaginous,  7 

connective,  7 

elastic,  7 

epithelial,  7 

fibrous,  7 

gelatinous,  7 

muscular,  8 

nervous,  8 
Titanophis,  500 
Toad,  485 

horned,  503 

metamorphosis  of,  477 

poison  of,  475 

spade-footed,  484 
Tomocerus  plumbeus,  364 
Tooth  shell,  257 
Torpedo  marmoratus,  422 

occidentalis,  422 
Tortoise,  510 

Touch,  organs  of,  in  Crustacea,  291 
molluscs,  270 
Toxodontia,  600,  629 
Trachymedusae,  62 
Trachystomata,  478,  487 
Transmission,  law  of,  11 
Trematodes,  structure  of,  146,  163 

development  of,  147 

pupa  of,  149 
Trichina  spiralis,  169 
Trichocephalus  dispar,  169 
Trigla,  443 
Trigonocephalus,  499 
Trilobita,  young,  323 
Trinucleus,  young  of,  323 
Triton,  478 
Trivia  calif ornica,  259 
Trochilus  colubris,  551 
Trochosphere,  259 

of  polyzoa,  186 

of  worms,  147 


718 


INDEX. 


Troekus,  development  of,  264 

Trout,  452 

Trunk  fish,  462 

Trygon,  424 

Tubularia,  60 

Tubipora,  85 

Tunicata,  development  of,  203, 211 

structure  of,  196,  215 
Turbellaria,  142, 162 
Turdus  migratorius,  556 
Turkey,  wild,  546 
Turtle,  green,  510 

hawkbill,  510 

loggerliead,  510 

sea,  510 

snapping,  510 

soft-shell,  510 

swamp,  anatomy  of,  506 

tortoise  shell,  510 
Tylenchus  scandens,  170 
Tylos,  306 

Typhlocolax  acuminata,  145 
Tyroglyplms  sacchari,  360 

ULOCYATHUS  ARCTICUS,  80 
Umbel  lularia  greenlandica,  86 
Ungulata,  600,  629 
Unio  complanatus,  244 
Urchins,  sea,  117 
Urodela,  478,  484,  488 
Urolabes  palustris,  170 
Ursus  americanus,  616 

arctos,  616 

maritimus,  616 
Urus,  612 
Uvella,  32 

VARANUS,  504 

Variation  of  species,  672 

Veliger  stage  of  molluscs,  252,  259, 

263,  266 

Velum  of  rotifers,  176, 178 
Venus  mercenaria,  249 
Venues,  characters  of,  138 
classification  of,  238 
Vertebra,  395 


Vertebrata,  characters  of,  389 

classification  of,  630 

brain  of,  392 

ear  of,  405 

eye  of,  404 

hair  of,  403 

limbs  of,  396 

notochord  of,  393 

scales  of,  403 

skeleton  of,  395 

skull  of,  397 

teeth  of,  401 

Vertebrates,  relations  of  ascidians 
to,  207,  214 

molluscs  to,  241 

worms  to,  214,  219,  229 
Vespertilio  subulatus,  591 
Vinegar  worm,  170 
Viper,  499 
Vipera,  499 
Vitellogene,  147 
Viviparous  fishes,  444 

reptiles,  495 

sea-urchins,  121,  122 

starfish,  110, 114 
Vorticella,  39 
Vulture,  548 

WALRUS,  614 
Wapati,  608 
Wasp,  380 
Water  bear,  361 
Water  flea,  299 
Watering-pot  shell,  250 
Wax  wing,  555 
Whale,  591 

fishery,  594 

sperm,  593 

bone,  592 

white,  595 

Whale's  tongue  worm,  219 
Whelk,  268 
White  ant,  367 
Worms,  138 

flat,  141 
'  fluke,  14G 


INDEX. 


719 


Worms,  nemertean,  210 

parasitic,  145, 146 

phosphorescent,  237 

round,  163 

strobilation  in,  144,  145 

tape,  153 

thread,  163 

trematode,  146 
Worm,  whale's  tongue,  219 


Wren,  555 
XIPHOSURA,  324 

ZEUGLODON,  595 
Zoantharia,  79,  91 
Zoanthus,  79 
Zoea,  313 

Zoogeography,  16,  658 
Zooids.  202.  210 


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